Hot Compost – Composting in 18 Days

Regular composting, also known as “cold composting”, involves placing a variety of organic materials in a compost bin, enclosure, or even just in a large heap, and leaving it there until it breaks down several months later. It’s a very slow process and typically takes 6 to 12 months. It can be sped up by turning the compost, that is, moving around the material at the bottom of the heap to the top and vice versa to mix it up and get more oxygen in there, but it’s still a long wait.

The other approach to composting is “hot composting”, which produces compost in a much shorter time. It has the benefits of killing weed seeds and pathogens (diseases), and breaking down the material into very fine compost. In contrast, cold composting does not destroy seeds, so if you cold compost weeds, any weed seeds will grow when you put the compost into the garden.

Cold composting does not destroy pathogens either, so if you put diseased plants into your cold compost, the diseases may spread into the garden, hence the common advice not to (cold) compost diseased plants. The other issue with cold composting is that you end up with lots of large pieces left over in the compost when the process is completed, whereas hot compost looks like fine black humus (soil).

One hot composting method, the Berkeley method, developed by the University of California, Berkley, is a fast, efficient, high-temperature, composting technique which will produce high quality compost in 18 days.

The requirements for hot composting using the Berkley method are as follows:

Compost temperature is maintained between 55-65 degrees Celsius

The C:N (carbon:nitrogen) balance in the composting materials is approximately 25-30:1

The compost heap needs to be roughly 1.5m high

If composting material is high in carbon, such as tree branches, they need to be broken up, such as with a mulcher

Compost is turned from outside to inside and vice versa to mix it thoroughly

With the 18 day Berkley method, the procedure is quite straightforward:

Build compost heap

4days – no turning

Then turn every 2nd day for 14 days

Composting Materials and the Carbon-Nitrogen Balance

In the hot composting method, the ratio of carbon to nitrogen in the compost materials needs to be between 25 to 30 parts carbon to one-part nitrogen by weight.

This is because the bacteria responsible for the composting process require these two elements, in these proportions, as nutrients to construct their bodies as they reproduce and multiply.

Materials that are high in carbon are typically dry, “brown” materials, such as sawdust, cardboard, dried leaves, straw, branches and other woody or fibrous materials that rot down very slowly.

Materials that are high in nitrogen are typically moist, “green” materials, such as lawn/grass clippings, fruit and vegetable scraps, animal manure and green leafy materials that rot down very quickly.

If ratio of C:N is right in this technique of fast, aerobic (uses oxygen), hot composting, the compost will break down to the same volume. This is in contrast to slow, anaerobic (without oxygen) composting that happens in a compost bin, which drastically reduces in volume as it rots down.

Many ingredients used for composting do not have the ideal ratio of 25-30:1. When using hot composting methods, you need to make an assessment of how quickly materials decompose, and then use a blend of things that rot quickly and things that rot slowly.

Composting materials with a very low C:N ratio of 7:1 would rot very quickly, because they are high in nitrogen, eg. fish, this decomposes very quickly

Composting materials with a very high C:N ratio of 500:1 would take a long time to decompose, because they are low in nitrogen, and need to be broken up, eg. tree branches

For example, if the C:N ratio is too high, you can lower it by adding manure or grass clippings. If the C:N ratio is too low, you can raise it by adding cardboard, dry leaves, sawdust or wood chips.

In trying to understand what C:N ratios are about, it may help to point out that all plants have more carbon than nitrogen (remember, they get their carbon from the carbon dioxide CO2 in the air) so that is why the C:N ratios are always greater than always above 1:0.

Below are the average C:N ratios for some common organic materials used for composting.

The materials containing high amounts of carbon, but low in nitrogen are considered “browns“

The materials containing higher amounts of nitrogen are considered “greens.”

Here are some C:N ratios of some common composting materials:

Browns = High Carbon

C:N

Wood chips

400:1

Cardboard, shredded

350:1

Sawdust

325:1

Newspaper, shredded

175:1

Pine needles

80:1

Corn stalks

75:1

Straw

75:1

Leaves

60:1

Fruit waste

35:1

Peanut shells

35:1

Ashes, wood

25:1

Greens = High Nitrogen

C:N

Garden waste

30:1

Weeds

30:1

Green Wood

25:1

Hay

25:1

Vegetable scraps

25:1

Clover

23:1

Coffee grounds

20:1

Food waste

20:1

Grass clippings

20:1

Seaweed

19:1

Horse Manure

18:1

Cow Manure

16:1

Alfalfa

12:1

Chicken Manure

12:1

Pigeon Manure

10:1

Fish

7:1

Urine

1:1

Anything that was once living can be hot composted – and I really do mean anything. All manner of things, including strange additions such as wool and cotton clothing, bones, leather boots, even things like “roadkill”, ie. dead animals, but these have to go in the very centre of the heap to break down properly. There’s no trace of the original ingredients when the process is complete! Remember, the greater the variety of ingredients, the better the compost, because it will have a wider range of nutrients in the final product.

Basically, if you want to to get started in a hurry, aim to use 1/3 Manure and 2/3 dry carbon materials. It will work. Just pile alternating thin layers of greens and browns until you end up with a compost heap that is 1 metre square and a bit taller than that. There’s no real need to get caught up in the mathematics of precise C:N ratios. It’s more a matter of trying it our, though I can’t stress how easy it all is.

To illustrate the point, a friend with a small with only a courtyard (in a rental property) wanted to attempt hot composting, and I helped him out with the project. He gathered a wheelie bin full of fallen leaves from his local street, one wheelie bin full of weeds from his garden, purchased a small straw bale for the sake of it. I helped him collect a few garbage bags of cow manure from an urban farm. It took us under an hour to pile it all up in reasonably thin layers (under 5cm) of each ingredient to get a good mix.

It was his first attempt at hot composting, and in around 18 days, he had over 1 cubic metre of rich, dark, compost to use in his garden. You couldn’t distinguish any of the original ingredients in the final product either, and it had a very fine consistency. Best of all, it cost him next to nothing – the straw bale was just a $17 luxury, it would have worked just as well without it, and without it it would have cost absolutely nothing.

Just think that 1 cubic metre is 1,000 litres, and if you think how much you pay for a 30 litre bag of potting mix (over $10) here in Australia, you realise what value this entails.

Hot Composting, Step By Step

DAY 1

Mix together ingredients by laying then in alternating thin layers of “greens” and “browns”.

Wet the compost heap down very well so it is dripping water out of the bottom and is saturated.

Can put activator in the middle of compost heap to start off composting process. Activators include comfrey, nettles, yarrow, animal, fish, urine, or old compost.

To explain in more detail, when turning compost, move the outside of the pile to a spot next to it, and keep moving material from the outside to the new pile. When you’re done, all the material that was inside will be outside and vice versa.

Ensure that moisture stays constant. Put gloves on and squeeze a handful of the compost materials, should only release one drop of water, or almost drips a drop.

If it gets too wet, can spread it down, or open a hole about 3-4” wide with the handle of the pitchfork, or put sticks underneath for drainage.

DAY 6 & DAY 8

The compost heap should reach its maximum temperature on these days. As an simple guideline. if you can put your arm into the compost up to the elbow, then it is not at 50 degrees Celsius, and is not hot enough. Best to use a compost thermometer or a cake thermometer.

Need optimum temperature of 55-65 degrees Celsius. At temperatures over 65 degrees Celsius a white “mould” spreads through the compost, which is actually”fire blight”, an anaerobic bacteria. Temperature peaks at 6-8 days and gradually cools down by day 18.

Turn the compost heap over every second day (on day 6 and again on day 8).

If the compost pile starts coming down in size quickly, there is too much nitrogen in the compost.

To heat up the compost faster, a handful of blood & bone fertiliser per pitchfork when turning speeds it up.

If it gets too hot and smelly and goes down in size, it has too much nitrogen, need to slow it down, throw in a handful of sawdust per pitchfork when turning.

Using the this system, the Berkley method, methane is released from the compost.

DAY 10 to DAY 18

Continue to turn the compost every 2nd day

DAY 18

Just warm, dark brown, smells good.

When earthworms move into the compost, you know it is finished and ready, because it’s cooled down and full of nutrients!

Some important points to note:

Locate your compost heap in an area protected from too much sun or heavy rain, to prevent the compost from drying out or becoming water-logged and slowing down the composting process.

Space required for for your heap should be about 1.5 x 1.5 metres, and enough space in front of it to stand when turning the compost.

Water each layer until it is moist as you build the heap. After three or four days, give the compost air by mixing and turning it over, then turn every three days until the compost is ready, usually in 14-21 days. Remember, frequent turning and aeration is the secret of successful composting.

Turn the compost using a garden fork, or even better, a long-handled pitchfork.

In cold or wet weather, you can cover the compost heap with a tarp or plastic sheet, to prevent the rain cooling it down, since the water will penetrate into the core of the compost pile. Even though cold outside air will cool the surface, but not the core of the compost heap, by covering it, this prevents some heat loss from the surface to cooler outside air, and retains the heat within the compost heap better.

Happy composting!

Share this:

Like this:

275 Responses to Hot Compost – Composting in 18 Days

Beautifully & clearly explained . Thank you. Methinks you ought to be a teacher.
Of anything at all ! I suspect you love the process ? Especially PERMACULTURE .
[ I visited your back yard once with the NERP PERMIE mob. Most impressive, as we all said on the day. I have meant to say previously : YOUR concern about the lead sheet flashing around the chimney is misplaced – with all due respect. I guarantee that you could not detect a DIFFERENCE between water from the East face of the house and the west face. Consequently I suggest that NOT collecting all that water ‘cos of the lead sheet flashing is a waste. { I also heard that there was a second reason for NOT collecting same ! } ] Warm regards david hicks…..Eltham N.

Appreciate the supportive feedback. You’ve got it right, I do have a passion for training/teaching, trying to do a career change into this area! Would love to teach permaculture!

Thanks for the advice on the lead flashing, it’s quite common on a lot of old buildings as you know, and it is a concern for quite a few people. I seriously haven’t looked to deeply into the matter, namely because my tanks can only hold the water I capture from the garage roof (30 sq. m), don’t have capacity for the rest, that would come at a later date. There are a few other minor technicalities too, which I won’t burden you with.

I’m currently working on a food garden community project, and they’re also avoiding capturing water off a slate tile roof with lead flashing. There’s so much water there to be had…

I agree, it is a terrible waste not to capture the water. I would love to be able to do the testing or find some research on the matter, because it’s very common for people to err on the side of caution, and not capture water in these situations.

You’ve motivated me to go do some research and find some scientific research papers on this, because if you’re right on this, and I don’t have reason to doubt what you say, this will give immense reassurance to people in this situation, and increase the amount of water captured for productive use, rather than flow down the stormwater drain.

You’ll most likely see an article on this soon if my seearch goes well, thanks for inspiring me to look into this!

This thread spurred me to research. Lead in tankwater is a real consideration, this from a CSIRO study: “The rainwater collected from all three roofs with lead flashing contained Pb concentrations exceeding the ADWG (and WHO) maximum recommended values”http://www.csiro.au/files/files/pk7r.pdf

Quote: “an increase in carbonate promotes formation of more soluble lead carbonate complexes.”

There are effective water filters for drinking. Not much use for the garden.

Can you really make a compost without it shrinking? I’ve never done that. I think they produce a lot of carbon dioxide as the microbes metabolise, so you have to lose some mass. And the whole thing settles too so loses some extra volume. That’s my experience anyway.

Thanks, really appreciate the links to the lead in tankwater research, I was looking for this information as it’s a topic of concern for many people who wish to harvest rainwater from their rooftops, lead flashings unfortunately are quite commonly used on Australian rooftops.

With hot (aerobic) composting, you’re right, the process of aerobic decomposition will oxidise carbon and create cabon dioxide, the amount of carbon is reduced as all the available nitrogen is utilised and captured. The reduction will be ever so small if you have an abundance of carbon rich materials so nitrogen is not lost. If the compost heap is compacting down too much, you need to add more carbon-rich materials. Agreed, the volume will also reduce slightly due to the physical breakdown and subsequent compaction of the composting materials too. You’ll lose some volume, but nothing drastic, my guess is you’ll definitely always have well over 50% of original volume, possibly closer to 75%. It’s hard to estimate accurately because I’ve never measured the volume accurately, so my estimates are somewhat subjective. Compare this with slow anaerobic composting, where the you will only end up with 20% of the original volume, you lose around 80% of volume, that’s quite a difference! It’s quite disappointing with slow (anaerobic) composting to fill a 200L compost bin and end up with only 40L of compost, but it’s still something…

Love your work too, would most welcome the opportunity to teach a permaculture course together!

Hi Jason, thanks for your comment. There is no need for an external heat source at all, the bacteria in the compost heap generate the heat by themselves! They can generate so much heat that haystacks on farms which have gotten damp in the centre and have started composting can actually burst into flames! Luckily that won’t happen with the compost. The bacteria consume the compost heap as they multiply, and when they chemically break down the organic matter into simpler compounds, heat is released. This encourages the heat loving bacteria, which break down the compost even further. That’s the magic of hot composting!

Hi there. Great instructions! The only thing is, I’m based on the West Coast of Ireland. Its summer now and the weather is blustery and cool with sporadic sunshine. Will this quick composting system still work here or does the outside air temp affect how the bacteria generate heat? ie: will this weather slow down the process? I am a permaculture student and everyone who has passed on their knowledge of hot composting systems here in Ireland say it will be ready at the earliest 6-8 weeks after constructing. Do you have any thoughts or tips on this?
Thank you! Julie

The hot composting process is driven by the bacteria, they generate the heat through the decomposition of the organic matter in the compost heap.
The compost heap is normally covered with a tarp or plastic sheet, to prevent the rain cooling it down, since the water penetrates into the core of the compost pile.
Cold outside air will cool the surface, but not the core of the compost heap. The covering prevents some heat loss from the surface to cooler outside air, and retain the heat within the compost heap better.

I must confess, I can produce compost in my tumble bin in 6-8 weeks in winter here. It only holds 200 litres, not enough for the hot composting process, and it only gets warm.
I’m pretty sure a hot composting pile should still work in 18 days in even a cool summer.

Ok, here’s a few tips to keep that hot compost pile running hot in cooler weather:

1. Make the pile as big as you can, bigger compost heaps retain heat better than smaller ones.

2. Increase the amount of nitrogen sources (greens) in the compost

3. Add some very ‘hot’ sources of nitrogen, such as horse manure, chicken manure or coffee grounds

4. Insulate the compost heap to retain the heat – cover it with a black plastic tarp (not airtight though, it needs a good supply of oxygen) or any other insulating material, get creative!

5. Place your compost in a location where it is protected from the wind.

6. Situate the compost heap in a position where it receives full sunlight (north in the southern hemisphere, south in the northern hemisphere)

How do you manage to get cold/cool compost finished in 6 weeks?
I’ve been tumblimg mine for 2 months and isn’t even halfway there.
Do you use a similar C/N ratio as per hot composting and have you any tips for those of us who struggle to find space even for a 200l tumber and have no chance of building a big hot compost pile.
Very nicely written article btw
Gerry C

Thanks Gerry, the trick to getting cold composting in 6 weeks is as follows:
1. Processing – Feed all materials through a mulcher first, the finer the compost materials are, the faster they break down. I think this makes a huge difference. Otherwise, just chop materials quite fine with a garden spade on the ground (not in the soil, it will compact it!), or using secateurs or hedge clippers to chop everything up first while the materials are sitting in a large container.
2. Temperature – composting slows down in the cold weather, placing the compost tumbler in a warm spot speeds things up, and the 6 week turnover only happens during the warmer seasons for that reason.
3. Materials – use materials that break down relatively quickly, and use a good mix of materials. For carbon containing materials, pea sraw, lucerne, dried grasses, newspaper break down faster than heavy branches that are mulched and still consist of large, chunky pieces. Add lots of nitrogenous (green) material, this breaks down very fast. Ratios of carbon to nitrogen are the least critical in a compost tumbler, technically you could compost green grass clippings alone as long as you turn it daily, but it’s best to add a good mix of mterials to try to achieve the optimum C:N ratio. With too much excess nitrogen, you lose to much of the nitrogen from the compost to the air because there is not enough carbon to bind it.
4. Volume – try to get as much materials as possible to fill the compost tumber in one go, it will heat up a bit on its own, but not enough to make it a hot compost, so it’s still cold composting.

Ah, thanks a million for your speedy response – much appreciated. Will definitely use onsite horse manure to help heat pile. We also have sheep manure mixed with straw that I am hoping to use. Just wondering what your thoughts are on using bracken as a green? We have an abundance of. Some people seem to think that it doesn’t break down properly. I was also thinking of using it for capping the heap as an insulator under the black plastic.
Also I have often been told that having a particle size of 2.5cm3 is optimum – is this neccessary for such a quick system?
Will keep you updated as to the results of our test!
Thanks again, Julie

No, there’s no real need to break up the material into very small pieces when hot composting, the combination of heat and bacterial activity can break doen a lot of things that would surprise a lot of people. – materials added to the centre of hot compost piles that have broken down completely include such things as leather boots, woolen jumpers, and roadkill (dead animals). With the latter only clean bones are left behind. Breaking things up roughly is usually sufficeint. 2.5cm3 or one cubic inch is the particle size you get from a chipper (a coarse mulcher), which is what I use for cold composting. Chopping up the material finely increases the exposed areas in the material that bacteria can act on, naturally speeding up the process of breakdown and decomposition. It definitely always helps but is not critical in hot composting.

Also, bracken ferns can be hot composted. Normally they are allelopathic, that is, they release chemicals which prevent other plants from growing, but thankfully the hot composting destroys these substances. Bracken ferns are a good source of potassium and break down slowly to create an acidic compost.

Using bracken for composting or as a soil improver The young green fronds of bracken can be collected for the compost heap where they will rot down slowly, enriching the nutrient content of the compost. Bracken stems are too woody to be added to the compost or leafmould heap, unless they are first shredded or chopped into small sections.

Bracken produces numerous spores, but these seldom seem to germinate and grow in the compost heap. Small sections of the roots can regenerate, and therefore should not be used in the compost.

Dead bracken collected in autumn can be rotted down to make mulch, in the same way as tree leaves are collected and rotted down to make leafmould.

Bracken ferns are believed to be carcinogenic, the current opinion is that people working extensively with them are at an slightly increased risk so try not to breathe the spores when working with them, a face mask might be a good idea.

So we are on day 11 of our hot composting in a cold climate experiment. We turned it again yesterday and it is still quite hot – 55-60 degrees in places. On the first few turns there was evidence of slight white mould but only on bracken in the heap. We added shredded newspaper to counteract.
So yesterday, on day 10 turning, we became a little concerned at how all this material will breakdown into lovely ready to use humus. Though the heap is hot and obviously some breakdown is happening, most of the the ingredients can be identified as their orignial state ie: straw, comfrey, hay, bracken etc.
I am wondering if we are on track or what condition the materials should be in on day 10?
I have taken photographs if you would like to have a look at how its doing.
Thanks again for all the advice and support.
Julie

If the temperature is in the 55-65 degrees celcius range, it’s on track, it should be OK. You’re only half way there right now, the breakdown of the material speeds up as the bacteria multiply exponentially, and there is a lot more of them to consume the compost materials!

Remember, around day 8 is when the temperature peaks, the next 10 days is the ‘slow bake’ period that will literally cook all the ingredients and break them down so they won’t be recognisable. The heap will be hottest in the centre, and the outside will naturally be cooler, which is why you turn it, so the outside material is put into the hot centre to break down. As mentioned in the article, if it starts to cool down, you can heat up the compost by adding a handful of blood & bone fertiliser per pitchfork when turning.

Please let me know how it goes after the 18 days, as I’m sure many people are curious how the process works in cold contitions.

What an interestingly well written site. I seem to fall into the notorious 10% of people who still have things to learn and add to my 50 yrs. of trial / error frugal gardening..

Born and bred in the N. Texas sparsely wooded black-land native grassy prairies, between ‘temperate zones” ranging from well below 0 degrees F to 114 degrees F, I chose to Zeriscape about twenty years ago, having learned from a N. American university -who’d successfully beaten the dreaded weeding/ watering drudgery with the right formula utilizing local available free materials and recylables.

[I’ve nearly died with every sort of compost formula’s molds,
fungus, and failed results, heavy labor, suggested DIY contraptions, and guesses, learning that few are designed for this zone/ temp
fluctuation and unpredictability/ toxicity we have here in city water, air pollution, [GMO/ hybirdizing of seeds], chlorine-gassing of most retail-sold vegetables and fruits, ignorance of “recommended pesticide useage’ by so-called ‘local experts’, laws growing agianst local organic farming, wrong and/or omitted important information resulting in greatly compromised immune systems of my large urban corner home and yard, as well as my slightly oversized but weakened, aging body! It’s enough to make an old gardener to give
up.

Have I? Nope. Like Thomas Edison, I have learned from hundreds of things and ways that don’t work ! It’s been a full circle of back-to-
basics/ Garden of Eden– thinking, greater common sense -regardless of ‘latest ideas’, and I now have a wonderful organic biosphere with VERY few, if any, pests or diseases, and several crops that have both grown and encouraged me to use all I have observed, re-thought, analysized, and concluded…to my full advantage, thanks to the Grace of God !!

The frequent feeding of the birds, squirrels, and observation of the advantages to having them,I more fully appreciate my variety of lizards and non-agressive ants, as God helps to balance it all. I’m having good success with top of ground, non-turning, cold composting, with the local vermi-culture/ beetles/ a few wasps/ and refuse from my wonderful, fat 3yr. old house-hen, 4 yr. old house rabbit [both contained in large waist high cages-cleaned-daily], along with a treasure-find of an electric ionizer/air freshener which totally eliminates any odors in ten minutes!

With weather extremes, black clay soil, frequent lawn-watering restrictions because of weather extremes?, and many trees/ shrubs, I’m trying to find ways to work within my boundaries, to preserve my VASTLY diverse landscape and strange EDIBLE native-plant takeover of my back yard. [Just thought I’d drop by and share from a reader of another region’s dilemma and to say,”. Keep up the good work; don’t give up, even on the white/black/green/red/ orange funguses !! or on learning. It’s both a challenge and a TRIP.

Updating, moved temporarily to the near countryside. Discovered that, in old home needing repairs, that my entire garden and flower beds were literally crouded with the largest most incredible GRUBS, not the usual ones, but gi-normous ones. Learned that my compost was so rich, plentiful, well decomposed that it was THEM who turned it into what I hoped it would be, but cannot use after all?

Downside: They continued eating the roots on everything smaller than a tree root!! Called the most reliable organic growers/retailers whose best horticulturist gave me the bad news: NOTHING so far is able to phase these creatures because they are particularly LARGE
and from ASIAN beetles [metallic variations on backside] that do NOT respond to Milky Spore. Since I’m all organic, I am searching frantically to find a natural deterrent or host to keep them at bay.

Any ideas or ‘latest news’ re these HUGE, nearly [small] chicken-leg sized grubs would be deeply appreciated. My yard is almost DIRT now and the most discouraging info says there is NOTHING I can do short of eliminating the dream of lawn/ bedding repair, and to plan
for ‘hardscaping’ instead.

So, unless some reader with additional info has a better idea, I’m going to pursue shadecloth under gravel meandering paths, repositioning my tub garden and bird baths, and streamline using what I already have but expanding into the lawn. According to the advice, I may even have to resort to artificial plants!!

Of course this situation may change if the coming extraordinary heat predicted for Texas is a reality, which just MIGHT penetrate deep enough to COOK whatever larva which may be lingering, getting hungry – having been so greedy as to eat both compost AND root system of the majority of my large corner lot!

It’s like a bad SCI-Fi movie, but God is good and may answer my prayers of distress. Afterall, He knows all things, including just HOW these beetles and grubs became so large, as well as what to do about it! What a dilemma!

I would NOT use ammonium sulphate in my compost, it’s a strange practice that non-organic gardeners are recommending, and I think it is a very bad idea.

Here are a few reasons to consider:

Ammonium sulphate is acidic, you don’t want ti acidify your compost.

It’s a mineral salt, so in quantities significant enough to contribute nitrogen, it will possibly be too high a salt concentration that will disrupt the bacteria and fungi in the compost pile ecosystem, and will probably slow the composting process down.

Compost is not just carbon and nitrogen, these are just the major elements that bacteria use to consititute themselves from as they multiply, but you need lots of other elements and substances in there too for bacteria to grow and break down the organic matter, and for the resulting compost to be useful as a plant food, which is ultimately what we want the compost for. Green organic matter contains all the other substances that aid decomposition.

Using a wide variety of ingredients creates the richest compost, which will be best for your garden. Using very few ingredients will make for a lower grade compost.

You have to pay for ammonium sulphate, and other than being unsustainable, having to pay for a nitrogen fertilizer is crazy, considering that is what all living organisms excrete as bodily waste!

I personally would discourage the practise, there are so many nitrogen sources freely available that the need to put chemical fetiliser in your compost would be hard to justify. It would really be easier to just urinate in the compost heap a few times if you needed to top up the nitrogen, seriously. You wouldn’t just use this as the only nitrogen source, since urine can have high sodium levels, we excrete salt this way, and you don’t want high salt levels in your garden either.

Just look at the list of nitrogen sources I have listed, there are 17 of them there, and there’s lots more available I haven’t listed, I’m sure some of these must be available.

Keep it all natural and organic, and you’ll be much happier, and so will your compost!

Thank You. I’ve been looking for a better explanation on Hot Composting. I just like doing things in such a way that they require less work from me. I saw a special that featured African woman in this village that collected all the food waste in a special roofed area where they had three piles: new, once turned, twice turned. As it composted the piles were turned and a stick pushed into them. To check the temperature they pulled out the stick and touched it to make sure it was nice and warm. The finished material was put into their gardens.
But, as we are running out of oil we should stop composting and look to get the most out of every calorie we can get. To replace composting collect all animal and human poop (pee too) as well as plant materials from the garden and kitchen. Slurry them (about like running oatmeal) and pour into a methane digester. What you get is methane and a high quality fertilizer. Two things where before you had one. More bang for every calorie.

Hello,
I was wonderin if you can collect your composting material over a period of time? I dont have that much material ready at once, but I throw all my kitchen scraps in the small bins I have for that in my backyard. Can I keep collecting the material and then start a big pile at once? Or can I use this method with small bins?
Thanx in advance.

Yes, you could gather your compost materials over time, and they will start cold composting where they are stored but that shouldn’t be too much of an issue, you will just lose some of the nitrogen content. Pile it all up when you have enough materials, then add some extra nitrogen materials (greens or manures) because nitrogen gets lost over time when storing the materials.

You can’t hot compost with small bins because you need a minimum of one cubic metre of materials to get the hot composting process running.

I have tried my first ever hot compost pile thanks to your excellent info. I wanted to share my experiences.

I’m in inner city Melbourne Australia

Because of lack of space I had to make a 1 metre square pen with chicken wire. I used veggie scraps, shredded green garden prunings, shredded dry leaves, lucerne hay, manure, molasses, partially broken down compost from my tumbler and smaller bin.

I built up the pile to 1 metre square in 3 stages because I didn’t have enough materials in the beginning so I think the highest temperature I got to was 45 deg Celsius. I added some blood and bone at the second and third stage because I thought being built up in this less than ideal manner a nitrogen boost could help raise the temperature. Don’t know if this was a good idea or not.

I lined the pen with hessian and then covered the top with hessian and a tarp. Because of the pen I couldn’t do your outside to inside turning method. My method was to shovel it all out and shovel it all back in again, mixing and breaking up clumps.

I got some white powder at a few stages on materials in the pile like lucerne hay. This was towards the top of the pile so I didn’t think it could be due to excess heat. I was wondering if it was because I didn’t damp this layer down enough as I noticed it was dry.

I used a mask over my mouth and nose when turning. But stopped using it towards the end when I didn’t think there would be airborne bacteria.

It’s broken down quite nicely although of course it took a lot longer than 18 days because the bulk wasn’t there. It smelt good at all stages. I now have a lot of small, fine twiggy bits throughout and I was wondering if the best way to deal with this is to sift the compost so I can use the broken down compost and save the twigs for the next compost pile. I was thinking this might be the way to go because now that its lost its heat the twigs will take a long time to break down.

I was interested in any thoughts on how to improve my process next time.

And was particularly interested in the best way to build up a bulk of materials. I have a small garden so gathering materials takes a while.

Am I best to shred everything as I get it and put it in my tumbler and small bin and then transfer it to the hot compost pen with new materials when I feel I have enough bulk.

Or would it be better to just let the garden prunings sit without breaking them down and carry on with composting the veggie scraps in the tumbler with the appropriate balance of dry materials. And then when I have the bulk, mixing them all into the hot compost pen.

I want my materials to be in the best shape they can be by the time I have the bulk to begin the hot compost.

Any thoughts would be most appreciated and thank you for such a great resource.

I was thinking of building a hot compost pile in my front yard before I build some large raised garden beds for veggie growing. There is space now but won’t be later. I was wondering if there is much smell. Would my neighbours find it a bit wiffy?

Thankfully, there is no smell at all once its all built. The first hot compost pile I built in a friends small backyard, we used bags of very smelly fresh comw manure we collected from a farm, when the compost pile was built and watered, no smell whatsoever.

I’m not sure I understand the 30:1 ratio. How is that achieved given the various ratios you show above. I mixed alternating layers of old compost, dried leaves, and manure to build my new pile. How can I tell if that will give the correct ration

Hi Scott, you can use simple cross-calculation for the ratio.
Assuming we’re only using straw (C:N ratio is 75) and chicken manure (C:N ratio is 12) for the compost (C:N ratio is 30), here’s how we can calculate it:

First we put the C:N numbers we know from our materials and the target in its places (x). Then we diagonally subtract the bigger number with the smaller. After that we multiply them horizontally, in the example straw’s C:N ratio is multiplied by the difference between target’s and manure’s C:N ratio. The two resulting numbers are the ratio for the ingredients. For this example we need around 2.5 part of straw for each 1 part of chicken manure. Based on the C:N ratio data, the ratio should be based on material’s weight, not volume.

However, I just know how to deal with two ingredients using this method. Anyone knows how to calculate C.N ratio of multi-ingredients?

Please note as what we need is the differences, negative number is not a problem. Ratio of 2.5 : 1 means we would need approximately 2.5 kg of straw for each 1 kg of chicken manure. However I only know how to deal with 2 ingredients with this method, anyone knows how to calculate ratio with multi-ingredients?

If the Berkeley method will compost dead animals, then surely you could safely add some humanure into the mix, which is full of like pathogens.

It would greatly encourage the composting of human waste if it was made know that it could be safely turned into compost in 18 days.

I suspect that no one wants to advocate this for reasons of cultural sensitivity or legal liability, but it’s time we thought through this apparent contradiction. The potential benefits are too big to ignore.

I’ve personally never seen hot composting used to process humanure ever, we can only guess at the reasons why. In rural areas in Asia whole countries us it unprocessed straight in the fields where food is grown, but they don’t eat raw vegetables, they cook or stir fry everything, so any pathogens probably get eliminated that way. That’s the cultural safety practice.

If the site is big enough, human waste can be processed continuously on site with a natural sewage treatment system – aerobic digesters that use bacteria to break everything down, then the resultant waste is passed through reed beds planted in gravel, then what comes out of this if fairly safe and is used to irrigate fruit trees. I believe Michael Reynold’s ‘Earthship’ buildings process all human waste onsite and use the outputs to provide water and nutrients to orchards near the house. Guess this is getting off the topic of composting though…

You can compost human manure you just need to make sure you get it hot enough. You are probably still best to use it for trees or bushes rather then using it on the vegetable garden. I have worked on an organic farm where a retired Environmental Scientist had a system for composting human manure. I read about along time ago how in New England there is some human manure treatment plants where human manure is broken down for compost (using bacteria) and sold to the public. Once any Nasty bugs have been destroyed the only issue I guess would be any medications people had been taking, which might be high in certain toxic minerals.

Thanks for the response. Yes, I know the three stage natural sewage treatment system as detailed in the Design Manual, but in relation just to hot composting, isn’t it interesting that no-one utters the “h” word?

I have the videos on-sale at the Tagari site of the PDC given by Geoff and Bill in Melbourne in 2005. In it, Geoff goes through the complete 18 day system. He also tells anecdotes about using the system to compost a wallabee, a duck,and road kill of various kinds. Never, though, does he mention humanure, nor does anyone ask him about it. Curious.

Unless and until I hear otherwise, I’m going to assume that the temperatures reached by this system are plenty high enough to render harmless anything in reasonable amounts of humanure composted in this system.

As I mentioned in a previous answer – “The compost heap is normally covered with a tarp or plastic sheet, to prevent the rain cooling it down, since the water penetrates into the core of the compost pile. Cold outside air will cool the surface, but not the core of the compost heap. The covering prevents some heat loss from the surface to cooler outside air, and retain the heat within the compost heap better.” I’ve updated the article to add this information, as this is an important point, so thanks for asking. Short answwer is no, covering is not a bad idea if you want to retain heat and prevent the heap getting waterlogged from rain.

If the heap is getting fire blight, it might actually be getting over 65 degrees celcius, depends if your thermometere is accurrate enough and long enough to reach the centre of the compost heap without digging it open. Leaving the top cover off for a while will coll it down a bit.

Your mix includes all the right ingredients to supply carbon and nitrogen, you just have the ratios correct, if the heap shrinks in size, add more carbon, if it’s not breaking down, add more nitrogen

Do you know where I can get a picture of fire blight? Maybe what I’m seeing isn’t fire blight, because it seems worst on grass, for example, glass left inside the lawn mower will get white stuff on it, too.

How can you tell if the pile is actually shrinking? Our pile has a good chunk of dry straw/hay, which tends to hold a lot of air, so it’s hard to say if the pile is settling or actually shrinking.

Hi. I have been attempting this method with two large piles. One 8cu meters of horse manure and straw and the other 40 cu m of chicken and wood shavings. They are tarped with black vinyl. The average outside temp in the day is 38c. I turn them with a backhoe. If I don’t turn for 4 days the pile temp will go up to 55-60. The problem is that when I do turn the temp drops to 47 or so and takes a few days to build back up. Thanks!

Thanks for the idea of ducks for the beetles that produce the ginormous grubs I have….soon to be new beetles! Problem with having ducks is that there is a local ordinance against them, and they must be fed daily, which is impossible since I’m living temporarily away from the home/garden while it gets upgraded/ remodeled as I can pay for it.

I LOVE ducks, and there are plenty in this city at the local parks, but they need both space and water, which I don’t have…even if the city allowed them in the neighborhoods.

True story from a casual acquaintance of ours who described finding a duck nest full of hatching eggs ..but without the mom: He took them home, nurtured/protected/raised them, only to have neighbors call the local police about their noise.

He said he had hoped to get them far enough along to release them in the park so he went to court and lied about the situation, saying, “The report you received was all wrong. That wasn’t noise from ducks but from DOGS!” They believed him, buying a little more time, but the neighbors persisted until police visited and took the ducks. Hopefully they released them rather than ate them!

Great article. I have two big piles of organic matter that I’d like some advice about. First, five bags of hedge clippings that might have some bittersweet in them–do I count them as green or brown? Right now its seems to be both. Wait until it’s all brown? I also have one precious bucket of horse manure that I thought I’d mix with food scraps as starter. The second pile is mostly forsythia that I cut down a couple of weeks ago, and as careful as I was, its even more likely that there’s bittersweet and Japanese knotweed in that pile. It’s basically a giant pile of branches. The good news is that since I’m constructing a woodland garden, I’m don’t even want perfectly fine soil, I just don’t want it to sprout demons.

Don’t wait for the green material to dry out and turn brown, you’re losing valuable nitrogen that way, carbon can be found very easily. Turn the whole lot into a huge hot compost pile to kill off all the weeds, and try to break down all the branches into smaller pieces however you can, mulch them, mow then, cut them up with a sharp spade – the compost works better when all the ingredients are broken down into smaller pieces.

Thanks. I kind of decided to “split the difference” with regards to the pile of hedge clippings. By that I mean I’m just not up for hacking up all those twigs. If you’re not familiar with the obsequious American hedge, you should know the twigs are pretty springy, going at them with a hoe wouldn’t work. I’d guess they’re 70 percent nitrogen; add in the leaves on the twigs, and my 2 m around pile might be too green if it weren’t for the larger twigs and the fact that it did die down a bit. Now it’s a 1 m tall twiggy donut with a horse manure-food scrap center! On Sunday I’ll turn it for the first time and decide then whether to add some cardboard.

My “bittersweet” neighbor has expressed some dissatisfaction with her cardboard and branch yard, so I’m going to leave it be.

Have just retired to the beautiful and remote Creuse department
in the Limousin in France. Have bought a 6 acre plot about half is mixture of mature oak and Beech, there is a lake of about half an acre and the rest is neglected long long grass which i am very slowly taming with strummer and mower. We are vegetarian and plan to start growing as much as possible next spring so am composting everything in sight as fast as possible to help fill raised beds. I am passing everything apart from grass cutting through a broyeur (shredder/chipper) so apart from the cardboard “removal boxes” its all very small. Two heaps so far about 4m2 each. The first i didn’t water enough so was running at about 35-40C The second I did and its at 65-70C, even 60C just 2-3 inches in – both have the same sort of mix. I turned the first heap today and watered as I went so expect temperature to rise. My problem is I have a bad back and the turning today which took about 90mins has left me with a lot of pain. I just cant see me repeating this on a 2 day turnaround, especially with several heaps. I would appreciate some advice to ensure readiness for next spring with the minimum of back pain! Thanks for a brilliant article.

Hi Chris, I would use smaller compost heaps, something closer to the size recommended in the article, around 1 metre square and a bit taller than that. A 4m x 4m x 1m pile is huge! That’s back-breaking work in anyones language, sound like something you would tackle with a front-end loader!

Smaller heaps are much easier to turn, around 15-20 minutes. Since you have to complete turning a heap once you start doing so, if you have several smaller compost heaps, they are much quicker to finish, so you can have a rest much sooner, that way the work is not as tiring and drawn out as turning one big heap.

Furthermore, by having multiple smaller piles, you can have a good rest after finishing each one, and when you are refreshed and re-energised, you can tackle the next. Thos allows you to spread the work out over the length of a day. For example, you could turn one heap in the morning, then another a few hours later, and so on.

Ah-hhh, our dreaded Texas summer is cooling down, but “the whole state has been plagued with mosquito-carrying West Nile Virus, causing a fairly large number of deaths.” Being so efficient, the city officials? or some authority has sprayed the entire STATE with ‘relatively harmless chemicals’ THREE times over a few weeks, causing a noticeable dullness of life in everything living.

It certainly put the skids on gardening hopefuls, and likely gassed
the many compost piles in the making with their concoction of only God knows what! [ Right away we found a poor dead Morning Dove who’d been feeding from the neighbor’s tossed bird seeds. So much for “harmless”.] Now I’m wondering how many more creatures will go the way of the bees -which have all but disappeared here ov er several years now!

My grub problem has not changed, yet the lawn in the temporary
home I’m renting has signs just like my other home-in-repair of grubs beginning at the edges of the lawn!!

With all of the genetic modifications/ mutations/ hybrids/ cloning,
even science [and Monsanto] likely doesn’t know or care what all they’ve altered/ created, much less how to rid our land of such things. We’ve sent more soil samples to the state agricultural extension center for analysis, waiting for some suggestions before blow-torching the remnant sparse stubs of well-established noxious weeds, wild carrot and wild garlic, which the omnivorous zombie grubs seemed to have rejected!

Yes, this sort of global bio-manipulation tends to make one pessimistic, frustrated, as well as outright ill. Although there must surely be myriads of researchers who have hopeful suggestions, but our arms and pockets are fast becoming empty for such challenges that are not of our own making/ budgeting.

The lawn responded to the first application of “recommended” [against my better judgment fading fast] Golf Course chemical fertilizer….for about a month, but our cheering it on, watering to near indebtedness to the city utilities, manicuring to an ‘exact science’, the results is nearly the same as before we started.
Luckily our property is not at all the only affected one.

Thanks to you, Julie, for the duck suggestion last July, but our city deed restrictions/ homeowners’ association refuse to permit us to have such helpful creatures within the neighborhoods. I still have my house-chicken and mini-Rex house-bunny in lovely large well-built rolling cages, but cannot let them freely roam outside, even inside my fence, because of the wild creatures the city protects – and which are attracted to and eat such animals. We have Owls, Hawks, O’possum, Raccoons, occasional foxes, Coyotes, abandoned domestic and exotic animals turned loose when someone moves, and hefty resident rats which are said to eat
the feet of chickens as they sleep!

So why am I writing? Just in case someone runs across another
soul like me, who might have an alternate solution to the blow-torch, [which would only take care of the tough dry stalks which we have also considered spray-painting GRASS green! lol If some of the local landscape companies can tint their seeded foam, it would be a big temptation even for you!]

Wish I could send a photo of it but we still have a few large spreading and tall old trees making a photo near-impossible. Hum-mmm, anyone know whether too many fallen acorns can ruin lawns over the years? We’ve always just mowed over them. They likely just fed more grub-bellies, right? Wouldn’t this scenario make a good video/board game : “Conquest of the Zombie Grubs”
with a sequel: “Protectors of the Zombie Grubs”.

[My grandson would likely want to develop this whole concept since his goal is to be a computer animation programmer of new games for teens and young adults. He’s currently reading every Anime book he can find for ideas. I’ll suggest this to him tomorrow and have my cellphone camera set for his laughter!] I may as well laugh, since I’m nearly out of tears, hair, and money!

Oh, might I suggest that NO one add litter-box residue [fresh or otherwise] nor ‘roadkill’ to their compost, because of the good possibility of diseases. You were just kidding, right, when you mentioned, “anything” can be added to the hot compost?

Our good neighbors began a compost pile the lazy way by just tossing all grass and a very few veggie scraps into a pile over a couple of years. [ It became the S.W. distribution of flies, rats, and whatever else since it was, to my knowledge, never turned by hand, but did indeed turn to blackest dirt.]

My son agreed to build their new fence when he built mine, with the understanding that he’d single-handedly move their pile to fill in our holes left by larger tree roots, to which they agreed.

Within a few weeks, one of the few veggie scrap SEEDS sprouted and grew the largest, most delightful Acorn/ Winter squashes we’d ever seen . I collected six large ones, stopped by to share with them but they’d gone on vacation, followed by our doing the same, and never got to see them before we had to eat them. What a wonderful surprise with a supportive message: Seeds can indeed
survive most bountifully any compost pile, neglected or tenderly tended. I have chosen to be MOST careful to prevent my adding seeds of any sort to the next pile on the horizon.

No, seeds do not survive hot composting, what you’ve described is cold composting, and yes, some seeds will grow from cold compost, which is why, as a rule, you should not cold compost any weeds with ripe seeds.

The best article on hot composting I have ever read. It all makes sense now, thank you so much!
I now understand that our heap is too high in nitrogen due to the large quantities of grass clipping plus chicken manure. It is getting very hot and getting fire blight. It is almost like it burns itself out and then cold composts from that point on. We ended up with some reasonable compost in the end but it takes a long time and wasn’t all fine and unrecognisable like you describe. Definitely going to do it this way from now on.
The only bad part with doing it properly is having to go out in the pitch dark at night to turn the heap. The perils of working full time in the city I guess.

Dear sir: thank you for a very clear and concise article on hot composting. I have lived in Asia for 22 years and I’m developing a system for composting of humanure into humus for home and industrial agriculture in developing countries. My UDDT system separates human solids and liquids for several reasons & you finish up with two vital products in humus & NPK (urine) In India alone there are 600 million people a day who open defecate in fields because there is no (and never will be) organised governmental sewage collection system. Therefore collecting and utilising human waste products on a micro and macro scale has huge benefits in terms of ecological, geological, economical and human health and dignity aspects. I came across your wonderful site because I heard of hot composting and wondered if it could be utilised for humanure?
A couple of points about the western phobia about growing vegetables in human ‘poop’

If you think you are growing vegetables in human waste you are not; you are growing in organically rich humus, which, when properly processed through aerobic thermophillic composting has killed off pathogens at a temperature way beyond what the human body takes to kill of its own pathogens; in addition, it has also gone through the vermiculture process. You should worry about using industrial ‘fertiliser’ a.k.a. toxic waste, not humus a.k.a. organically rich compost.

Is it safe? Yes, according to WHO standards. http://www.who.int/water_sanitation_health/wastewater/gsuww/en/index.html
Faecal pathogens are dead after one week of composting at a sustained temperature of 122 f°. When processed / composted properly from humanure to humus the compost contains no harmful pathogens. (WHO) Thermophillic composting often produces temperatures of around 150 f°.
In addition I have been in contact with several members of the SuSaNa forum who have been growing in humus and using NPK (urine) for agriculture & salad plants for many many years.

I will share with you once I (eventually) have my web/blog up and running. You should definitely put a programme together and go out and teach it in schools / community centres etc. We can save on fuel, carbon and land fill etc etc by taking personal responsibility for our waste products. Spread the word!

Composting human waste is a very good idea. I think a better one is to put both kitchen waste, urine and human waste into a methane digester to produce methane for cooking to not cut down any more trees and reduce indoor pollution and you also get a very high quality of fertilizer that you can put right on the land. This is something some Chinese have used for hundreds of years to keep their field fertile without soil depletion.

I am trying to hot compost using shredded oil palm fronds which are half dried, peat soil as bulking agent and chicken manure. Can i use your method with these ingredients?
Will adding some compost activator help in the process?
I am located in johor, Malaysia with tropical temperature and climate.
Appreciate your reply.
Thanks.

It should work fine, as long as you have the right amounts of carbon and nitrogen containing materials, the bacteria will do the rest. Using a compost activator always helps, you can use comfrey, yarrow or nettles. Or you can pee into the compost heap! Adding a small amount of mature compost always helps to ‘inoculate’ the compost with the right bacteria. Give it a go and let us know how it goes!

Hi,planning to build a hot compost while winter will come soon is it a good ideea?! Covered,outside or covered ,inside a part of greenhouse wich will not be used during the winter? if yes,what kind of manure is better to use,fresh or from the last three months? of course,will try to use activators but the problem is fresh manure or not? the temp will be soon below 30f(0 celsius)…
will try to increase the ratio of carbon till 40:1,or should i let it 25:1 ?! will be cows and horse manure….
From Romania,with admiration and respect for your work !
Cris

Hi Cris, to be honest, I’m not sure if the hot compost pile will cool down too much during such cold weather, because our weather never gets that cold here, so I would only be speculating.

Covered up, and inside a greenhouse should work, and it will warm the greenhouse too for a short time. Fresh compost will be the ‘hottest’ because it contains the most nitrogen, the aged compost will still work well though.

Don’t change the C:N ratio, because that is the ration that is used to make up the bacteria’s bodies, and it’s their activity that generates the heat. Excess nitrogen won’t be utilised and will probbaly just be released from the compost heap as ammonia.

It’s really a matter of timing, if you you can make the compost (in 18 days) before the weather gets very cold, then all will be fine to build it outside with a cover. If you want to make hot compost in freezing weather, all you can do is try and see what happens.

In Permaculture, we work with the cycles of nature and the ‘wild energies’ moving through our system/site – and one of those energies includes the natural heat from the sun. I would assume you would have the most materials to compost in autumn with leaf fall from deciduous trees, and green waste from your summer annual plants after harvest. This would give you some time to compost before the winter cold set in, and you only meed 18 days to do it!

First attempt failed in glory! :(
Succeded to rich few spots of 55 grdC ,but ,lack of personal presence for aeration ,…leading to a expected failure !
Now,spring is come again ,with fresh energy and more achievements!
Keep in touch!

I gave it a go. With so many autumn leaves it was silly not to. Tempatures this week are below freezing and I think it’s stopped the process. Yesterday while turning the pile for the 5th time on day 13 I didn’t see any steam like I had the times before.

I have been covering the pile. I’m curious if there are things I can try to get it going again?

Great article! Thanks. I have a question:)
Will pomegranate peelings break down as quickly as other “green” materials? It happens that I have plenty of them but also need quickly a lot of compost. Was wondering if it’s ok to use the peelings or should clip dome grasses? I really need compost in 3 weeks and as I have no experience in gardening/composting I thought I would ask:)

When hot composting, everything will break down! You’ll need to mix them with other ingredients as per normal hot composting practice. If done right, the ingredients will just vanish and create fine, dark, rich compost.

“Ratios of carbon to nitrogen are the LEAST critical in a compost TUMBLER. Technically you could compost green grass clippings alone as long as you turn it daily, but it’s best to add a good mix of materials to try to achieve the optimum C:N ratio.”

[Emphasis added.]

~~~~~

I’m preparing a 58-gallon black plastic drum (once used to ship cucumbers in brine) for composting, and have a question about the air circulation.

There’s so much emphasis on the C:N ratio on the Web, but John Paul, Ph.D, P.Ag. (http://www.transformcompost.com/about-us.php), a noted compost researcher, also told me that in a TUMBLER, that ratio is less important than air circulation and moisture content. This confirms Blackthorn’s comment above.

Dr. Paul was too busy to give me specific advise about the number and size of holes to drill into this 58-gallon tumbler, so I’d appreciate your advise about that.

I intend to turn this barrel on its side and put in and take out the materials from the “top” end, which is a “bell jar” type design allowing one to open it by screwing and unscrewing the (entire) top.

I’d like to drill the holes only on the “original” top and bottom. Is that a good idea? (I don’t want to drill holes in the “original” side because that will allow all the “compost tea” to drain out onto the ground, and I want to drain out the “compost tea” into a special bucket only occasionally, using a single hole (with an on/off faucet fitting).

Definitely drill holes only in the top and bottom so you can collect the ‘compost tea’ liquid.

My tumbler compost bin is a commercial (bought) one, it has four holes on the outer edge of each top and bottom end, 8 holes in total.

The ‘holes’ are 3/4″ (19mm) in diameter, but aren’t really holes, they are a line of five slits that make up a circle shape. I’m guessing that’s to stop flies and other undesirable insects from getting into the compost bins.

However you make the air vents, make them up with a series of small holes if you can.

Hi,
We made a compost pile with mostly sheep manure mixed with some left over hay that was mixed in from what the sheep had eaten. But in the end it was mainly manure. We didn’t add much else. The pile is 6 ft high and 10 ft wide. We turned and watered it once a week for around 6 weeks. The highest temp we reached was 122 degrees and then the temp went down to 110 and we can’t get it much higher. It is turning black and the sheep pellets are decomposing. With our organic certification it is required that we reach 131 F minimum for 15 days. But we haven’t come close. I realized we probably didn’t have enough carbon so we added two bales of straw to see if that would help. But so far the highest temp is 110 F. Should we add more straw in layers between the current compost pile or is it too late because a lot of the manure has already broken down? We have the pile covered with a tarp as well.

Hi Tina, that’s because sheep manure is low in nitrogen compared to other animal manures, plus side is that it won’t burn your plants, minus side is that it’s not the best source when you need lots of nitroge. Hence the recommendation to use a mix of ingredients in your compost. Hope this helps!

If you could answer my Nov. 25 post, I’d be much obliged. This weekend I’ll be setting up the compost barrel system and need advise about the wisdom of drilling the “circulation holes.” On Nov. 26, Mary Schwarz at the Cornell Waste Management Institute advised against drilling any such holes and instead to ensure that the materials I use — she recommended “wood shavings” that contain much air / oxygen in lieu of “saw dust” — are carefully measured with the coffee grinds in the proper proportion. But I’ve never heard of a compost tumbler with NO circulation holes!

I’ve answered your original comment, please see above. The tumbler bins, and all compost bins for that matter, rely on aerobic composting, they definitely need oxygen, otherwise they go anaerobic and stink! You definitely need air vents!

I would only keep it airtight if I was using a bokashi fermenting anaerobic system, but that doesn’t need tumbling. The point of tumbling the compost, moving it, turning it, etc, is to get air into the mix to speed up breakdown!

Thank you for your responses. I’m still confused about where are the holes in your composter, since “top” and “bottom” and “side” are unclear to me. Can you tell me what is the model and manufacturer of your compost tumbler? That way, I can go and see a picture of it on the Internet / web site of the company.

Ah! Thanks so much! I can see from the video and the photo that the holes are precisely where I’ll put mine — on the “ends”. The difference in the “Tumbleweed CompostTumbler” and my home-made tumbler is that, if one considers all tumblers to be a “cylinder,” the “Tumbleweed” operates (spins, tumbles) “vertically” and mine will operate “horizontally.” The video doesn’t discuss the problem (or benefit, depending on one’s viewpoint) of excess moisture inside the tumbler that may create “compost tea” that must be drained off. One manufacturer of a “horizontal” design tumbler solves this problem with two “compost tea” drainage holes in the door. See http://www.compostumbler.com/StoreFront/product/original-compostumbler. I will not have any such “door” however; I will have the same sort of screw-on, screw-off “top” as “Tumbleweed” and will drain off any extra water or “compost tea” with ten holes, drilled in a line along the bottom of the barrel, each about 1/4 inch diameter, with a “catch basin” underneath to “catch” any “compost tea.”

Since my compost tumbler drains out the liquid from the lids, especially in the rain, I simply collect the compost tea by placing a plastic garbage can lid (the thick solid ones) underneath it, works well!

If you exclude rain water, how much liquid typically drains from your tumbler? That is, how much water does your compost accumulate on its own? Does warm weather cause much or any of it to evaporate through the circulation holes?

Thank you!!! It sounds like I was going the wrong way with adding straw and increasing carbon. You mentioned low nitrogen for sheep manure and thus low temp, so if the pile with the sheep manure has already decomposed quite a bit is it to late to add things with more nitrogen ? Would it be better to start over with a new pile of more of a mix of ingredients to get the hotter temps of between 131-170 and to use this current pile as a manure amendment rather than compost? Or can I add more ingredients now?

Many university extension service offices say that all living things have the necessary bacteria to cause decomposition.

However, the primary components for my compost tumbler will be two: wood shavings and coffee grounds, and neither of these seems particularly endowed with bacteria.

Where I live, there are few chicken farms but many horse stables.

Should I expect any more success (i.e., progress in composting) by adding chicken or horse manure? If so, how much if my barrel is 58 gallons (220 liters) and I put into it, at one time, all ingredients?

Also, how full should I fill my tumbler by volume? one-third? one-half? two-thirds?

“Variety is the spice of life…” and is essential to a good compost too! Manure would be more like a third ingredient, which will be better. I’ve alreay mentioned the compost activators/starters in step 1 of the instructions.

When using a tumble bin, I aim to fill it almost all the way to the top, usually about 75% full all at once, you need to leave enough space for it to be able to tumble and mix around.

I started my hot compost BEFORE finding this site. I have included layers of rich dark soil between my green and brown layers. The soil had many beautifully large earth worms. Am I going to cook them or will they retire gleefully to the bottom of the heap as the temperature increases?

Hi Chris, I’m guessing that if earthworms can rise to the surface when the barometric pressure drops (signalling rain) so they don’t drown, they would hopefully similarly respond to increasing temperatures and burrow down into the cooler soil. This is only speculation on my part!

I am calculating the carbon to nitrogen ration of composting cardboard and coffee grounds. I come up with .54:1. Does this mean .54kg of cardboard for every 1 kg of coffee grounds? Is their a volume formula out there and not a weight formula? thanks for the quick reply.

Basically, if you’re working with volume, to simplify things, aim to use 1/3 green/nitrogen containing materials and 2/3 dry carbon materials. In other words, one bucket of nitrogenous material to two buckets of dry carboniferous material.

For example, cardboard has a C:N ratio of 350:1, and coffee grounds have a C:N ratio of 20:1.
If you want to work it out mathematically, you need to take into account the moisture content too, which complicates things. I found an online C:N ratio calculator at http://www.klickitatcounty.org/solidwaste/fileshtml/organics/compostCalc.htm and using your ingredients, with a simple 2:1 of cardboard to coffee, the calculated C:N ratio was 40:1, which is still ok, the fact is they rate coffee as 13:1, while my sources ghave it at 20:1, resulting in a final ratio of 41:1. Really, there is a lot of variation between materials, so it’s not exact. This example just shows how the ‘rule of thumb’ of two buckets dry : one bucket green can be fairly accurate.

thanks for the quick reply. that makes sense. Would the 2 buckets brown 1 bucket green work for leaves, too even though leaves have a c:n ratio of 60 to 80:1? I have also read 2 greens to 1 brown. anyway, thanks for the reply.

If you can turn it easily, then it’s not too big, otherwise make several heaps of a manageable size.
If you turned it with a front-end loader, it would be very easy! That’s how they turn hot compost on a commecial scale!

I am composting shredded leaves and poultry manure. when i plug in 1 cubic foot of poultry manure to 20 cubinc feet of shredded leaves into the compost calculator the computer says 1 part poultry manure and 20 parts leaves and am only getting a 23:1 carbon nitrogen ratio. so this means 1 bucket of poultry manure to 20 buckets of shredded leaves, seems like too much carbon. any clarification would be nice, thanks

What a great post. I started my pile 4 days ago but realized I seriously underestimated my horse manure so the pile was too small. However, I still added urine to activate the pile. So 3 days ago, I picked up some more horse manure and added it to the pile- layering- with more straw (aged straw) and leaves. I am not sure that my pile is big enough since of course the laws of physics do not allow for exact blocking of the pile and it often settled and slipped during the process. So I am really unsure if my volume is correct. Also, I live in New Mexico and we have had a really cold winter these past few weeks so the poop was cold, the leaves are a bit wet, and the straw was cold. I took the pile’s temperature with my 20″ thermometer today and yesterday- it remains at 32 degrees F. Am I doing something wrong? Is it supposed to read around the “hot” temperatures during the first, second, and third days?
Thank you so much,
Adrienne

If temperatures stay low any heat is immediately lost and the pile does not cook, heat up enough. Wait until you have warmer temperatures and in no time you will have compost.
Don’t forget you can add all of your kitchen waste too and I highly recommend it. Stirring a pile will also help speed up the process of turning it into great soil.
I love composting.

One more thing: Everyone can continue to add to their compost pile, bin or whatever throughout the winter. There is no reason to not continue just because it gets cold. (Extremely cold climates are an exception.)

I helped a friend build a hot compost pile when we first learned about it, and it completed in exactly 18 days, that’s why I wrote the article!
Mind you, we ended up with a cubic metre of compost, which was a lot for a tiny courtyard!

Thanks for the article! I read through almost all of the comments and I didn’t see anything about when the compost can be used. Most of the articles I’ve read have mentioned that you should let your compost “cure” after it finishes otherwise it can burn the plants, and I’m wondering if you have advice on that.

I’m in cold Minnesota and despite the 10 degree weather my pile is already 80 degrees, 3 days after putting it together! It’s getting pretty smelly though, so I’m guessing I need to add some more straw to my pile, and that might cool it off quite a bit. Oh well, not too bad for this time of year!

The compost is ready to use as soon as it’s finished, in 18 days from when you first construct your hot compost heap! All properly made compost will not burn plants and should not require any curing process. I can only imagine that if a compost uses a lot of really ‘hot’ manures that haven’t broken down properly, it would be like adding the manure straight to the plant, and some nmanures will burn plants. You do’y have to worry about this at all. Properly made compost is gentle on plants, you can plant seeds and seedlings into it without any concerns.

Is there any way to “supercharge” your compost before putting it out into the field? Any value to adding biochar, urea, or anhydrous to the process? If adding compost to alkaline soils, ph 8.0, is there a process to make your compost slightly acidic? Thanks for all the good work.

No need to do anything to your compost, it’s already “supercharged” with life, it’s packed with lots beneficial living organisms which will enrich the soil and help your plants grow, and compost contains lots of nutrients in natural concentrations or levels that won’t burn your plant’s roots.

If you add any chemical fertilizers such as Urea or Anhydrous Ammonia directly to the finished compost (or even into your soil) you’ll kill all the life in the compost (or your soil), which kind of defeats the purpose of using compost and gardening organically in the first place.

Fast/hot composting creates a slightly alkaline compost, slow compost creates a slightly acidic compost. If you want to make the soil acidic, don’t mess with the compost, just use plenty of mulch over the soil surface which will slowly break down, and if you really want it very acidic, for growing blueberries for example, mulch heavily with pine needles around the plants.

Compost works on its own and doesn’t need biochar either. Just dig you compost into your soil or place it on the soil surface, but under a thick layer of mulch so the soil life can get to work and the nutrients can leech into the soil.

Hi, I have just found this site, brilliant advice! I have a hot compost heap on the go now, I am not particularly worried about it taking 18 days, as I can’t gather the materials to replenish in 18 days either. So my question is, will my pile naturally cool down as it becomes ‘ready’ (or as the nitrogen runs out)? Or can i keep it hot by adding more nitrogen periodically and is there any benifit to this? Is there a definitive way to be sure that the composting process is ‘over’? Thanks for the advice! Jon

There is no need to gather more materials to ‘replenish’ unless something goes wrong, most of the time, once the compost heap is built, nothing else needs to be added, it only needs to be turned as described, and when it cools down after the 18 days, it will be ready. There is no benefit in keeping it running hot any longer, when it’s ready the bacteria will have used up both carbon and nitrogen, not just nitrogen alone.

After 18 days, you will beyond any doubt know it’s ready, as the compost will be fine, dark, and rich, much finer than any slow/cold compost you’ve ever made.

If, after the 18 days, you want to keep composting, I recommend you leave the completed compost alone and build a second compost heap!

We have a very large manure pile on our acerage, mostly cow, some chicken and goat and lots of hay and straw mixed in. We had to bury our cow in the pile when she died last week (no diseases) and I am wondering how I could go about breaking this all down as quick as possible, it is also winter still here, -20c sometimes at night. I would prefer not to have to disturb her body as it decays or stir up any smells it may give off….can anyone help?

I have a three challenges that could benefit from some group think–not enough nitrogen material, no ready access to water, and cold weather. What I have is plenty of leaves and snow, a trash bag of bunnie poop and carbon bedding, and about a bushel of–what do you call it after worms do their work? It’s great soil, but does it qualify as “nitrogen” for the purposes of hot composting. And if I layer snow in with what I do have, will it melt and make my pile wet enough? I think I’m going to start on Friday, USA. Great site, thanks muchly for keeping it up.

Day 1. Ok, so here…I’ll find a way to post a picture–it is; a layered heap of oak leaves, snow, and grass mixed with bunny poop and worm castings. The down side is the lack of water, and maybe too small a heap. The up side is the high quality nitrogen. I’m not really sure if I got the ratio or thickness of the layers right. It’s supposed to rain/snow and so that could be a good/bad thing. I dithered quite a bit over whether to put it under the wooden fire escape and kind of split the difference by putting it near the border on some rocks and a slight slope. So, if there is too much water it will drain and if not enough…well, that’s the rub…and I guess I can’t post a pict. Maybe on my blog. I’m way to excited about this.

Hi, great article. I am trying my hand at composting and gardening for the first time ever. I bought a plastic bin and have layered dried crushed leaves with kitchen scraps (many of which were already breaking down) and coffee grounds in it. I wet it and mixed it. I rent and hope to move soon which is why I didn’t dig a whole. Will hot composting work this way and should I keep the lid on or off?

I have grass clippings available at the moment, but not much else. Would it be an option to layer the grass with completed compost rather than laying it with other carbon sources like straw and manure etc?

I do have some cardboard and newspaper, but when I did cardboard a while ago, I found it to be a pain when trying to turnover the compost, so I wasnt going to use it again. Any one have any good methods of the best way to incorporate newpaper and cardboard without spending to much time on it?

Paul, I agree, the problem w/newspaper and cardboard is that it’s time consuming to shred. I tried this w/slight success: at the end of last summer I put a layer of cardboard at the bottom a of drainage ditch by my downspout and then put a layer of leaves on top of it. I didn’t turn it until a couple of weeks ago. It was partially decomposed. Since a lack of ready access to water has been a barrier to me hot composting, I might try putting my hot composting pile in the same ditch. I know that doesn’t really solve your problem, but that’s what I did w/my cardboard! A

The trick with newspaper is to take the sheets and crumple them into tight balls without tearing them up, they help with aeration of the compost this way and provide a source of carbon. Works great with regular cold composting too!

With cardboard, tear it into pieces by hand, it shouldn’t take any longer than 15 minutes to tear uo enough cardboard to have more than enough for a cubic metre sized compost pile.

A word of caution, I wouldn’t use too much corrugated cardboard though, the glue contains boron, which is meant to be only a trace element in the soil, too much is toxic to plants.

To be honest, it’s actually rather strange to suggest that sources of carbon are hard to come by. In a planet filled with carbon based life forms, they’re everywhere around you, all the time. Gather fallen leaves in the autumn/winter period and put them aside for composting. Twigs, branches, dried plant matter and garden prunings work well as a carbon source. Break your materials up into small pieces it if you can – use a mulcher, put it on the ground and mow over it, or put in on the ground and chop it up the best you can with a spade.

Remember, the greater the variety of materials that you use, the better the compost. I would seriously discourage the idea of attempting a ‘two ingredient’ grass and cardboard or grass and newspaper only hot compost. You might as well just spread the lawn clipping straight on your garden if there are no weed seeds in it, or compost the straight lawn clippings in a tumbler style compost bin that you spin around by hand.

If you’re going to make the effort to make hot compost, it pays to make the effort to gather a range of ingredients first.

It wouldn’t work as well to use compost bays that wall the heap on three sides when hot composting because with the Berkley hot composting system you need to be able to take all the compost from the outside of the heap first (from all around it) and then pile it up in the new spot to create the centre of the new heap. After that you then put the most composted material that was in the middle of the pile on the outside of the new heap. Essentially, you’re turning the compost heap inside-out! With three sides enclosed you can only access one side of the outside of the compost heap, so you wouldn’t be able to move all the outside material first.

Fantatic information – many thanks !! I have a question I hope you can help with – I am planning on starting a heap and have plenty of carbon (dried leaves) etc and sheep / chicken manure and was wondering if I could dispose of my out of control blackberry bushes in this process as a green nitrogen source ? Would this be effective or suggested to do, or am I putting myself at risk of spreading the bugger further in my garden ? My thoughts were to layer it as a green source alternating with the manure and dried stuff and even pour a bit of urine on it for good measure ?

The blackberries should break down nicely in a hot composting system, but you’ll need to add extra nitrogen as the blackberries are a fairly low source of nitrogen, they would fit in the category of “Garden waste” with a C:N ratio of 30:1, too low to use on their own as your sole nitrogen source. You’ll need to add lots more nitrogen as the dried leaves you’re using are a fairly high carbon source with a C:N ratio of 60:1.

Many thanks again for your advice – I am very new to this all and find your site excellent. I will take on board what you suggest with the extra nitrogen – might get some extra cow or horse poo in addition to my chicken and lamb stuff I already have from my own farm. My main concern was the blackberry canes mulched up and used in the mix would flourish (being so evasive) instead of breaking down. I would probably suggest that cold composting them would not be advised, but wasnt sure about hot composting. If I can put them to good use like this – then all the better !!!

I love this info! Our school currently uses a method very similar. And have 3 hot composts and a vermicompost. We also use pencil shavings once a week. I was reading your blog re water collection. We are collecting condesation runoff from the air conditioning units.
Thanks for your great insight!

Hi I found your site by pure luck – my husband and I are building a compost heap and I have quite a lot of brown leaves and some green freshly mowed grass. My question is I also have some raw meat that I would like to compost in this heap. I have read your instructions and know to make layers 5cm thick each and to put kitchen waste in the middle. After 4 days when I am moving the heap do I continue to keep the meat/fish in the middle of the heap each time I turn it? I also have prawn heads and shells and the shells of mud crab. As we are in Autumn now I understand I will need to keep the heap covered with a tarp. Would you advise me if I should use the raw meat and seafood in the heap please

If the compost gets hot enough, like it should, you shouldn’t be able to see any of the meat/fish/scraps in the middle, it should have disappeared! Make sure it’s all cut up very fine so it breaks down faster! Make sure you also have enough of a material rich in nitrogen between all the layers, such as manure, blood & bone or something similar, as grass alone as a nitrogen source might not get hot enough.

I admit that I was sceptical about this method of making compost. I am therefore delighted to report that it worked. I did not worry about having a precise carbon-nitrogen ratio mix: most of my raw material (approx. 3 sqm) was grass clippings, with about two months’ worth of kitchen scraps; some garden refuse (twigs, leaves, weeds, and branches cut into small pieces); and some shredded paper. I followed the instructions almost exactly otherwise, except that occasionally the interval between turning the pile exceeded two days. I also watered the pile after turning it each time.

The inside of the pile grew exceedingly hot during the composting process, as expected. I doubt that the white substance that appeared (see earlier posts) is actually “fire blight” – but even if it was, it did no harm, and it disappeared in due course. The pile was typically smelly after having been turned each time, but this smell only lasted a few hours (at most), and was attenuated with watering.

In three weeks, all of the raw materials (except for some twigs, woody roots and bits and pieces of other wooden matter) had turned to compost. The temperature dropped considerably and there was no smell; it was impossible to identify any of the original material. The final stage in the process – from the point where there was still some identifiable grass clippings, leaves and paper, to the point where I only had warm, friable compost – seemed to take place overnight and occurred very late in the process. I noticed only a slight loss of volume overall.

I began using the final product almost immediately. I screened some of it to use as a turf underlay, and used the remainder – including twigs and other matter, all of which I am told will eventually break down – on various garden beds, most of which have a poor soil base. I have no doubt that my plants will thrive.

A few points:
1. The twigs, etc., that do not break down might be profitably re-used in subsequent compost production (ie, if you prefer not to use them on your garden bed).
2. This video (http://www.youtube.com/watch?v=-Jm-c9B2_ew) demonstrates how the heat generated from a small compost pile was able to heat water for 500 hot showers!
3. The regular turning of the heap is very good exercise!

just read your great article and may apply it a compost heap i have just finished preparing. I am working as a partial teacher here in a district outside of Kathmandu city Nepal. Trying to help the Nepalese people move away from chemical fertilizing back to natural methods. if you know of any permys that want to help out in Nepal send them my address, these people could really use some teachers in this field.
i definetly will be trying out your method on the next heap i build thanks mate

Is it ok to add moss/grass clippings that have been treated with ferrous sulphate? Had a guy come out to look at our lawn as it had been left to its own devices for over a year (We have just bought the place), It was strimmed back and treated with ferrous sulphate as we had more moss than grass!

2 weeks after treatment, we are still raking out the moss and old dead grass i was hoping to use this in some way rather than have to burn or dispose of it as there is quite a lot of stuff (1/2 acre of lawn). Would it be more carbon rich than nitrogen given that its mostly dead?

Would it be suitable to mix the resulting compost with some sand to make a good top dressing for the lawn?

Hi Neil, You can definitely compost the moss and grass, the iron sulphate should be fine, it will simply make an iron-rich compost. If the lawn clippings are mostly dry, they will be richer in carbon, you might need to add a bit of nitrogen rich material to help it break down. You can use the compost straight as a lawn top-dressing, add teh sand only if you need better drainage.

Hi love the hot composting method but i must admit that i wasnt as diligent in turning the pile for about a week after the first ten days we were bombarded with rain for about 4 days so i had my pile covered with a tarp. When I uncovered the pile i saw mushrooms everywhere so i turned the pile and watered it as usual but the next day a mushroom head was poking out. I wanted to know is ths something that I should be concerned about and what could I improve upon to reduce the amount of mushrooms in the pile. I have also heard of mushroom compost so could the sight of mushrooms be a benefit. My name is Joseph just a beginner composter that is looking for some answers.

The mushrooms are just breaking down the carbon-rich materials in the compost heap. You’re making mushroom compost! If mushrooms are growing, it indicates that the heap has cooled down too much, because mushrooms won’t be growing in a hot compost system that is cooking away at 55-65 degrees Celsius!

Hi! Your information is great!! I have some questions… Can I put manures (horse) straight in the compost pile, or do I have to leave it until it dries before adding to the pile? And is it reliabe to use sawdust for the compost?is it possible that it has some chemical products on it?
Thanks!

My understanding is that microorganisms are what make a compost pile work, and microorganisms are found in soil. So why don’t you recommend adding soil to the green and brown materials in the compost pile? Thanks.

I’ve been making compost off and on for years, using various methods, but I don’t think I’ve ever succeeded in making a proper hot compost heap, so I’m now quite excited at having a go at this, having seen the proper way to do it.

I have a slight worry though. I haven’t seen any mention (I don’t think) of vermin (typically rats), which can often be a problem with cold composting, even using a bin of some sort. I would have thought an open heap would be more prone to vermin, or does the high-temperature keep them at bay?

With thanks and best wishes,

Mike (from the UK, where the “summers” seem to have been getting colder and wetter in recent years!).

Hi Mike, at the temperatures of hot composting, any rats or any other vermin that get into the heap when you first build it will be cooked, decomposed and thoroughly composted – you’ll be lucky to find anything but the shiny clean bones!

Hello again, I have now made about a dozen hot compost piles, and never had one fail, winter or summer. I use used pet bedding mixed with whatever green I have, it’s so easy and an amazing process! Excellent site. My question is, I want to heat my polytunnel over this winter with a succession of hot compost heaps, but usually my pile is about 3m cubed, so I want to get this down to about a metre. Is there a way I can make my piles more ‘efficient’ by using different materials so I can get the volume down? Thanks for your help (:

Great to hear your success with hot composting, thanks for sharing! No need to make your compost heap smaller, you can tap into the heat of the bigger pile and direct it to your polytunnel enclosure. If you do a search on the web you’ll find instructions for building hot compost water heaters that can be used for providing hot showers, etc. They just use a long heavy duty hose coiled under the compost heap. Instead of showering with the hot water you can have it circulating through a long copper pipe or a copper coil (which radiates out the heat) inside your polytunnel enclosure, and connects back to the hose as a big loop, like a solar hot water heater.

High Blackthorn, what a great site, I love it.. I’m a long time organic gardener and have cold composted for many years. I have a 2 bay set up where I build up the heap progressively using any waste I can get from the garden and kitchen inter-layered with soil. When the bay is full I move it top to bottom into the 2nd bay, aerating it and moving the oldest compost to the top. I get 3 bay-fulls (about 3 cu.mtrs) of good quality compost a year from the system and I am able to use it continuously as the second bay continues to break down. Its worked well but I really like the sound of the hot composting process and plan to start my first heap. I can get an almost limitless supply of wood chips from the local tip (accumulated waste from arborists), so I was thinking of using this as my carbon content and chicken manure as nitrogen. The woodchips are fairly course and I am wondering if this will work OK. I am using a lot of my organic waste from the kitchen and garden in my wicking worm beds these days, so there is less than there used to be for the compost heap.

Hi John, I really doubt that new coarse wood chips would lend themselves to hot composting as the only carbon source, the bacteria would have trouble accessing the carbon as it’s locked up in the wood and there is not much surface area for the bacteria to act on to start breaking down the material. My guess is that the heap would starve of carbon very quickly.

Also, making a two ingredient hot compost is something I don’t recommend, the finished product is only as good as the materials you put into it, the more the better for a more balanced compost with a wider range of minerals and nutrients.

You could re-mulch the wood chips to finer pieces and give it a try, but the end result won’t exactly be a fantastic compost unless you add more ingredients in there.

Many thanks for the feedback. It is appreciated, however I do want to make a couple of points.
First, I have been using woodchips in my cold compost for years without problems breaking them down, they are crushed in the chipping process which splinters them and increases surface area significantly.
Second, I have been persuaded recently that the main benefit of compost is that it supplies food for the soil biology. It is said that the diverse microorganism population of the soil breaks it down and provides nutrients to the plant in a form easily assimilated by them.
Humus is probably the most concentrated form of food suitable for microorganisms, hence my interest in hot composting, but in nature cold composting seems to be the way microorganisms are naturally fed. It seems to me that the origin of the compost is not so important as the micro-organisms attracted by it.
In my worm farms (built into raised self watering wicking beds) I feed the microorganisms with finely chopped kitchen and garden waste (A large handfull every 2 days). In 4 days the waste has been largely broken down by microorganisms with the help of composting worms. Burrowing worms distribute the microorganisms and their food into the plant growing area of the wicking bed).
A good article on this and related subjects can be found at:-

Hi John, excellent points, thanks for sharing! If the woodchips are not large hard chunks on wood, it’s fine. I use a chipper type mulching machine with a large slow turning cutting wheel and feed heavy tree branches through it, which I then cold compost like yourself.

Thanks Blackthorn, The link to this page went in well before the C:N list. They are both in my blog on Organic Gardening, and the list is in the article on “Compost” (What else?).
You can access them through a link in Wicking Worm Beds if you wish. Thanks again for your great blog, and the use of your C:N list. I am sure my blog visitors will get a lot out of them both.

Hi, great article. I am preparing a aerobic compost of mixing with 60% paunch (21:1), 20% wood chips (probably 226:1 or 400:1) and 20% of wood ash (25:1) for commercial purpose in winter season. Today (1st day) I recorded temp is 22C only. Was my mixing ratio wrong? If wrong, how to correct them now? Its open, no cover and rainy. pls advise. Regards, Jakir

Way too much wood ash, that would be very highly alkaline! Wood ash is only meant to be used in small amounts, 1/5 is way too much. Less wood ash, perhaps a greater variety of materials. What exactly is paunch, is that animal offal?

Hi, Thanks. Yes that is cow paunch. since that amount of ash is already in mix, so could I add some paunch to increase temp as temp is still low? I like to achieve a C:N ratio of 30:1. Pls advise accordingly. I did not found any weblink that help to calculate C:N of paunch.

Even though offal is high in nitrogen, it’s strongly bound in proteins, and it’s not very fine in size to have a large surface area. You need a source of nitrogen that is more accessible to bacteria to get the whole thing started, such as manure, or blood and bone, etc. Most often, meat is added to the centre of the heap in a small amount, in the form of road kill, bones with meat still on them etc. In this position, where the heat is most intense, the meat is completely broken down. Wood chips and meat is not a workable recipe for hot composting, it’s a way of composting meat scraps slowly in pits in the ground, which is the way farmers dispose of dead livestock, they dig a pit with a front-end loader, fill it with sawdust, put in the animal carcass, cover it with sawdust, then bury it with soil. The nutrients are returned to the soil slowly that way.

Thanks for the ideas and techniques under discussion. I make a lot of compost, using mainly the neighbours’ lawn clipping plus leaves, wee, chook litter and the odd lucky bag of horse manure. I scored a lot of “aggie pipe’, a ribbed perforated black plastic rigid tube that greatly speeds up composting. I just coil it in the Dalek-shaped compost bins (!) and use generously through the big heap. Compost near the aggie pipe matures sooner, I assume because of the oxygen it provides, and also the housing for worms. I highly recommend introducing aggie pipe through your compost, particularly if you have a bad back, as turning is obviated and moving the mature compost is easier when you extract these air tubes.

Great read! I have been a cold composter for years but I am how moving into hot in order to try to heat water for a shower! I have read other sites about the process but I am still curIous on how to attain the “hot” decomposition but have my system last for longer than 18 days. Also I am working in the tropics of Thailand if anyone has any recommendations for systems or adaptations. Cheers!

Thank you very much for such an enlightening explanation on how to hot compost. I want to let you know that I have a successful result from following your instructions. Although the size of my pile never quite reach 1.5 as required, still the core temperature heated up to around 150-160 F. The pile consisted of straw, dried uncomposted leaves from fall season, grass clippings from lawn, donkey & goat manure ( from a friend), garden weeds, kitchen waste. I used pee & some old garden compost to activate it. I am harvesting the compost today, it looks like a rich, dark brown heap.

Ok, noted and thanks. Have used your technique for past 6 months using different carbon sources and vareity of palm oil fronds. We add compost activator, liquified 20 litres to every heap. Compost activator has anti oudour and EM additive to it. For each heap, the finished dry weight is approx 870kgs. We are doing 6 batches per day for use in our 2,100 acre plot of oil palm, young and old trees. No chemical fertiliser as far as possible since plantation is beside national park reserve.
How do we post you pictures of our production using your method?
You have contributed a lot to us in terms of knowledge and tech support.

If the temperatures over 65 degrees Celsius you get ”fire blight” which is an anaerobic bacteria, to remedy add some carbon rich materials and turn the compost to get more air into it to and cool it down. Then continue turning as per the procedure.

Since the 90s I’ve used a modified Berkeley method that virtually eliminates turning more than one time.

With a ground base of 1/2 inch diameter brush, cut to 8-12 inch lengths approximately 6 to 8 inches thick, I made a series of alternating layers of first high carbon about 2-4 inches, topped with 1-2 inches of high nitrogen material, or add ammonium sulphate or urea sprinkled on.

Repeating this to the 3 foot high point, I add another 2-4 inches of short brush and then more C and N layers up to 6 feet high. In higher levels I mix the brush into the “C” layer. The turning is eliminated since air easily flows through the pile from the heat.

To slow the air flow I top the pile with soil or fine compost material. When finished building the pile I soak it well with water, and tromp it down if the material is to “fluffy.”

This produces top grade soil in two to three weeks.

For the outer material that does not get hot I simply screen it out and add to the next pile build. I’ve produced hundreds of Cubic yards of very fertile soil this way. It sells for top dollar, and makes a garden like you need to see to believe.

Plants growing in this soil are disease and parasite bug resistant and I use zero pesticides, and zero fertilizer for lush, large plants and vegetable yields.

Hi Angelo, Thank you for editing. However I still don’t know what the brush looks like. It still doesn’t make sense to me. WRT to the email address, I have used a disposable one whereby I can delete that address once I get a reply from ClaudeA.

Hi Claude, sounds like an interesting approach to composting, but how do you separate the cold composted outside material that will still have active weed seeds in it from the hot composted interior compost where any weed seeds would be deactivated?

I should point out that the purpose of turning the compost is not only to get air unto the mix, but to turn every part through the hot core of the heap to break everything down – pathogens, weed seeds, etc.

Being a farm boy, my concept of “weeds” from having generations of family and settings’ experience, is based on the fact that nothing is an unwanted plant – every plant has a beneficial part of the production.

In fact, I purposefully grow “weeds” just for the soil-production process. Jerusalem Artichoke is a noxious “weed” in my gardens, and yet I allow it to grow and multiply wild to use its awesome heavy stalk for part of the branch material in the compost pile.

Every “weed” is welcome to grow and thrive wherever it is not a nuisance, and when it is, or I am ready to build a compost pile, I have a ready supply on material.

I say “every weed,” so I do need to clarify. The only weed I try vainly to eradicate here is clinging burr. But, like all others, it manages to sprout all over from wind, bird and animal tracking, so i simply add all i pull to the compost.

Please re-read my pile-build procedure, Angelo, The outside material is separated out to go into the next pile. I use a horse stable, ten-tine fork, and for larger screening, I have an old wire and spring bed frame that screens out brush and un-digested larger particulates.

If some “weed” seed makes it through, the 100% compost soil of my garden is so giving I merely pull the “weed” out, roots and all with a little tug.

The moisture trapping and awesome nutrient content of the soil produces very heavy yields, and plants grow very late in the season, I pick raspberries to just past frost, and root vegetables keep in the soil all Winter, The rhubarb, mints, parsleys, perennial herbs, garlics, onions, and other biennial and perennial plants thrive here in the Puget Sound winters, and I pick Siberian Kale every month except for those with most days below freezing.

Artichoke grows to seven feet, and each stalk yields up to six hand-sized globes. I sow garlic like one sows a lawn, and the large bulbs crowd each other but with adequate water, the yield is amazing.

Dahlia loves this soil, and since “weeding”: is so easy, they grow without any competition to very large proportion. Ditto Glads and lilies.

The point I’m making is that “weeds” are merely a mental issue, and once their management is put into proper order, become a very beneficial ingredient to a wonderful garden!

I have numerous pix of various stages of building piles, but it will take some doing to reform them suitable for the blog.

To use a few words meantime, picture tree and bush branch trimming piles where branch limbs are under 1″ in diameter extending on out to the smallest stems and leaves. Cut these into 8 to 12″ lengths with all forked sections cut to the main stem, to make separation from the fi8nished compost easier.

Use this material for the ground layer, and the mid-pile layer, and I add some in finer materials that tend to clump together in thick wads.

The idea is merely to get and keep air flow in the pile, but not too much air, as it will dry the pile and halt the reaction.

The frequent pile-turning is VERY labor-intensive, and the brush adds air to the pile without the turning. It’s that simple.

As for destroying pathogens, one or two days at 140 – 160 degrees Fahrenheit destroys such things as chicken bones, small meat scraps, all finer plant material, and begins attacking the lignin component in woody material. The main source of destroying pathogens is not heat, though. The enzymes and living organisms in the hot compost pile – remember, oxygen is the worst enemy of all pathogens – attack the pathogens with vicious ferocity. Think of a bread mold on steroids.

Again, “weeds” are never an unwelcome part of gardening – every single plant adds a harmonious part to the symphony we gardeners enjoy – nutritious, bug and disease-free, ORGANIC produce!

Hi Claude, I agree with you about the weeds, every plant has a purpose! For us urban gardeners with smaller gardens, sometimes we don’t want an entire garden of lemon balm, hence why I like to use methods that take out unwanted seeds!

Some pathogens, which cannot tolerate high temperatures, are destroyed by heat, they are literally cooked, and yes, the complex compost chemistry does the rest, lots of enzymatic activity breaks everything down, it’s wonderful stuff.

Just curious, using your technique, which is a kind of hybrid hot & cold composting system, does your compost pile reduce in size or volume?

Hi Mike, if you use a good variety of ingredients in your compost, it will be more than adequate, considering that’s how trees have naturally grown for the last 370 million years, from composted material on the forest floor, you shouldn’t need to add anything else, especially not chemicals.

If you add chemicals to your compost you’ll most likely mess it up because the chemical fertilizers are simply salts in high concentrations and they kill the microorganisms that make composting possible.

If you need to add a range of micro-nutrients and trace elements to your soil or compost, add rock dust (such as granite dust from rock crushers) or seaweed extract (or just seaweed itself).

I followed this hot composting method a couple of weeks ago, but the composting process has not completed and I’m wondering where I went wrong.

I built the pile about 1.5 metres high in a cone shape in a spot that gets a few hours sun (this is at the end of winter in Melbourne, Australia). I used two thirds by volume dry brown materials, and one third green materials. The brown stuff was a mixture of dry leaves, pine needles, some partly decomposed fine wood chips/shavings (left after grinding a tree stump) and some newspaper scrunched into balls. The green materials were grass clippings, chopped up garden waste, some kitchen scraps and commercially packaged animal manure (mostly sheep but also some cow and poultry). To get it going I used some urine, liquid seaweed and mollasses.

I kept the pile moist and loosely covered with black plastic, and diligently turned it every two to two and half days, rebuilding the pile from the outside in.

It started off well – the material changed colour to a dark brown after it had been inside the middle of the heap and starting decomposing, and there was no smell. I didn’t have a thermometer but it seemed pretty hot in the middle initially (eg. after about day 6 it was too hot to put my arm inside the middle). It seemed to be on track until about 13 to 15 days in, when it cooled down but the material was yet to fully compost.

That was about 10 days ago. The heap is now dark brown and coarse in texture, and the individual components are still visible (eg leaves) and the process appears to have stopped. I tested the pH and it’s slightly acidic (6 to 6.5). There are no worms to be seen as yet.

I told my partner the problem was that he wouldn’t oblige with the urine and I had to do it myself with a container, but I don’t think that’s it.

I’m unsure (a) what went wrong (b) what to do from here. I need a whole lot of compost to improve my clay soil, which is poorly structured and low in humus. I’m planning to put in acid-loving plants.

Given this, I am not overly fussed about the coarse texture, but worried that if I use the partly decomposed compost it will draw nitrogen out of the soil.

Should I use it and hope for the best, or try to get it going again with more nitrogenous material?

Hi Sara, it sounds like your compost started off well, but cooled down too early. If the carbon source materials such as leaves are still visible, it would suggest that the compost heap ran out of nitrogen. I would try to get it going again with more nitrogenous material, you can try using ‘blood & bone’ fertilizer along with whatever other nitrogen source you’ll be adding, it’s extremely high in nitrogen. Also, try to make the shape a bit flatter, like a big cube or cylinder, a cone geometrically has the greatest surface area for the least volume, so you end up with too much material exposed and not breaking down. Hope this helps. Give it a go and please tell us how you go.

One direct benefit of this is the increase in earth worms feeding on the decomposing material. Where plants are growing in the soil the worms’ wastes are directly captured by the roots, and the health of those plants is exceptional

However, for clayey soil the critical issue is air-flow into the soil. To assure that directly turned-in material gets air, add woody, stemy branchlets that are mainly vertical in the soil and one end is near the surface.

The immediate results is that the soil can sustain some plants, and the long range effect is great, fertile soil in a year or tww, where material is added several times and the soil is naturally turned.

Farmers of staiky plants, lie corn, use this same principle to keep the field soils; organic content up, and maintain disease-free crops.

I have driven the machinery that buries such material – quite an impressive operation!:-))

Now, as for “brown” material that still has the original shape and some of the texture before hot composting, you will discover that this material is actually completely decomposed except for some of the ligins that hold the woody parts together. It is ready to support most all plant roots in this stage, especially when directly turned into the soil. In a year or two it will be finished in breakdown due to soil-borne activities, such as earth worms, fungus and molds, and the myriad of tiny creatures feeding on it.

Hi there, I like to make hot compost (aerobically) commercially for a large volume, using cow paunch (30:1), wood chips (400:1), wood ash (25:1) and chicken manure (12:1). Pls advise me what would be the ratio of ingredients? Very much appreciated.

If you know the % of water in each of the materials, you can use the Cornell Waste Management Institute’s – “Calculate C/N Ratio For Three Materials” online calculator at http://compost.css.cornell.edu/calc/2.html

I wouldn’t use too much wood ash, it’s highly alkaline!

If you haven’t got all the figures to do the precise mathematics, just stick to the basic formula for working with volume, to simplify things, aim to use 1/3 green/nitrogen containing materials and 2/3 dry carbon materials.

In other words, one part of nitrogenous material to two parts of dry carboniferous material.

In your case, I would try 1 part cow paunch, 1 part chicken manure and 4 parts wood chips. Use only small amounts of wood ash.

Since you only have one main carbon source, the wood chips, the ratios to use also depends on how much of the each of the nitrogenous ingredient (the cow paunch and chicken manure) that you have.

Try these basic ratios on a smaller scale and adjust ratios depending on your availability of materials, and results in composting. If the composting process shows it has too much nitrogen, increase the amounts of wood chips. If it is not getting hot enough or breaking down completely, add your nitrogenous ingredients.

Keep in mind that there is so much variation in the amount of carbon and nitrogen in any one ingredient sourced from different places or even different times, that you can’t calculate this exactly mathematically from the first instance. It’s a matter of experimenting.

Also with your large scale hot composting, will it be in a huge commercial closed vessel or composted on the ground in open air – this will determine how much cow paunch you can use. In open space, outside of an enclosed commercial scale hot composting vessel, you can’t have animal guts exposed to open air, you can only have smaller amounts in the centre of your compost pile when you begin, deeply buried in the core of your compost where it gets the hottest. The size and density of the woodchips will also determine how much paunch you can use, and how effective your carbon source will be. Large chunks of heavy, dense wood will not compost very easily.

My advice, test your ingredients and fine tune the proportions of each material with a smaller heap, then scale up after you can successfully hot compost on a smaller scale.

Depending on your budget, and with that scale of material it appears substantial, you may want to look into forced draft composting if for no other reason than to lessen the very strong likelihood that with those very fine particulate materials, and especially the entrails, oxygen flow to the innards of any pile will be severely curtailed.

Commercial forced draft composters also speed the production by several magnitudes of scale, producing finished soil in less than two weeks, and for many dairies, in one week or just days. Of course, moisture and temperature are critical factors, as combustion temperature can be reached in a matter of hours.

I am using a 200 litre compost bin rather than an open pile and am only able to get the temperature up to 37C. I would like some help to get more heat.

I am mixing up the C and N fairly well but maybe I have not enough C because the level of the compost keeps dropping a few inches a day.

Other thoughts I had were:
1) The first items I put in were not cut into very small pieces so maybe are rotting slowly. I am now chopping everything up as much as possible. Could the early larger pieces explain the low temperature?
2) The bin is 90cm high and the circular shape is 70cm in diameter ie much smaller dimensions than the article recommends. Do you think that this smaller capacity explains the temperature not getting any higher?
3) Turning the content of the bin is not easy. I am mixing it up as best I can, but can’t get to the bottom 30 m very easily. Should I consider emptying out by tipping the bin over and put the compost back more evenly mixed.
finally,
4) I am continuing to add materials (both household peelings etc and garden clippings – I am in Wales so am doing the start of autumn clearing of the allotment); do you think the adding of new materials is slowing the whole rotting process? If so, should I start a new compost heap (or buy another bin) and leave the first one to do it’s own thing (turning when needed)?

Many thanks for the helpful article. Definitely got the compost bug!! Even added some urine this morning.

The reason why the instruction specify that the compost pile needs to be of one cubic metre in size or larger (over 1000L) is because you need that much material to reliably reach the required temperatures. We’ve all heard about haystacks catching fire when they start composting, very large amounts of material can generate a lot of heat! A small compost bin, even a large one, simply cannot hold enough material to make a compost heap big enough that will hot compost. I have several compost bins, four 200L bins and a 400L bin for cold composting, and no matter what material I use or how much I fill them, they cannot hot compost.

Not sure why you use a bin, but it may be due to occlusion of air. Also, the finer the source material, the less trapped air – oxygen – there is. You might look into cold composting with a fungus mix for your operation. The fungus destroys all material – seed, bacteria, and lignins, much like hot composting.

Also, if there is enough air-oxygen, and the nitrogen is low, add a little ammonium sulphate of urea, or even blood meal to raise the “N.”

Also, fall leaves clump together in mats that block air flow, and exclude air entrapment. This is one main reason I developed the addition of brushy material and the smaller limbs and branches to allow for air flow. On a cool morning with the sunlight right, one sees a wispy steam rising from the top of a good hot pile with an earth or finished compost topping to partially seal the pile.

Thanks Claude for bringing up another method of breaking material down like hot composting, but with a cold composting system.

You can cold compost weeds in an airtight sealed container using the bokashi bin mix, this is a mix of lactobacilli, fungi/yeast, and phototropic bacilli (Lactobacillus casei, Lactobacillus planarum, Lactobacillus fermentum, Lactobacillus delbrueckii, Bacillus subtilis, Rhodopseudomonas palustris, Saccharomyces cervisiae) which is used to ferment food scraps. The fermentation process is very acidic and destroys weeds and weed seed. After two weeks the fermented waste can be added to the compost bin or buried in the soil.

“You can make your own “soil factory” in a storage tub: put some good soil on the bottom, add a layer of well-drained fermented food waste, mix well. Cover with a layer of soil and flatten. Cover with plastic or a lid to keep it from getting wet. After about 30 days, it’s ready for use as “good dirt“.

I donate about a day per week to make soil for a community garden in Seattle. The other day one gardener showed me his new experiment with this His hopes were for kitchen wastes, and meat-bone scraps.

I’m not sure how much pathogen reduction earth worm vermiculture does, but I would think that the soil these little creatures produce is full of similar fungi and bacteria. Pathogens are viciously attacked by oxygen-breathing organisms, and worms promote oxygen breathing flora and fauna, so vermiculture may be a viable procedure to produce safer material to add to the hot pile, or maybe use as is, which I know many do.

I’d like to learn about more ways to produce soil from different raw feed stocks. Each has specific nutrients that combine to provide plants with both health and disease / parasite resistance.

In my use of 100% compost for the garden growing medium, I see very little parasite and almost no disease, opposed to plants growing in the native soil. But I have not made an effort to determine what causes this.

I do have some slug issues, but the rough texture of the compost turns most away, and for the persistent ones I scatter diatomaceous earth around the few plants slugs insist on messing with. They do not cross the DE at all, and where it is on the plants they also stay off there.

Has anyone here experienced composting plywood, or other similar glued-together wood construction material? I was given quite a bit of thin plywood which is separating at the glue joint.

After reducing the size to about 12″ square or smaller, I have built a pile in layers of recent yard wastes – acorns, leaves and some composted leaves of last year, cardboard and paper, and hot material from the active compost pile.

With a few pails of water added to these layers and topped with active, hot compost, I’m hoping the Douglas Fir plywood will decompose by next Spring. I wonder if I should have added a commercial form of nitrogen, such as urea or ammonium sulphate to help the large amount of wood to break down.

If anyone has experience with similar material your advice is appreciated. Also, Angelo, did you see any mention of the fungus being used for woody material breakdown? I’ve seen piles of wood chips where fungus permeated the pile and rendered the wood into a softened form, but not into a completed soil-quality material.

The glue in plywood is urea-formaldehyde glue, which is toxic on account of the formaldehyde it contains. From the studies it looks like it takes 180 days (i.e. half a year) for the majority of the formaldehyde to break down in the first study. In the second study, 90% of the formaldehyde is broken down after 10 days of hot composting. It appears that it’s not completely broken down and considering formaldehyde is a known carcinogen, I would simply find less toxic materials to grow food with! Its not worth poisoning your soil for, considxering carbon based materials are everywhere, autumn leaves, fallen branches, newspapers, etc.

Fungi break down wood into soil, that’s their role in Nature, you can use shitake mushrooms to turn hardwood logs into lots of mushrooms and mushroom compost.

“Need optimum temperature of 55-65 degrees Celsius. At temperatures over 65 degrees Celsius a white “mould” spreads through the compost, which is actually”fire blight”, an anaerobic bacteria. Temperature peaks at 6-8 days and gradually cools down by day 18.”
Hello there from South Australia, I have made a pile at our school, it has been cooking for 7 days now and when tested today and the day before it was 75 degrees and today probably about 65.I had not measure the temp before this. Can it get too hot? And this white mould, is that a good thing or a bad thing. It has lots in the middle of the pile. I assume if I turn the pile now…it will heat up again and that is what you want? I have been told just to leave it. Perhaps add a little more water? It has a mix of roo poo, straw, blood and bone, lawn clippings and Lucerne hay. It gets incredibly hot, great to show the kids at school! Would appreciate advice, thankyou.

Hi Janelle, your hot compost is getting too hot! If it gets way too hot some of the bacteria that are more comfortable living at the lower temperature ranges get killed off I believe. Only add water if it needs it to maintain the correct moisture level. Please keep following the instructions, it’s still on track, keep turning it every second day, it will help cool it down, and you should have perfect hot compost by day 18. Please let us know how it goes!

Hi, I followed your hot composting instructions but the heap has cooled down now and is just warm. I can’t find blood and bone, I only could find blood pellets and these have not made any difference. Is there any other other quick fix to warm it up? It was going so well, it is covered as the weather is cold here in France. Best regards Katharine

Hi there
Firstly this is an amazing source of information and inspiration, thank you.
Secondly I am a total novice and have just started my first compost site. I am also awful when it comes to maths. So I was hoping you could help me.

Would you be able to give me a rough ratio in percentages? Hope that made sense!.

Again, thank you so much for building this resource. I used to be a secondary teacher and from this point of view you are excellent at communicating information that is accessible to a wide range of abilities.

Remember, we’re aiming for a C:N (carbon:nitrogen) ratio of approximately 25-30:1.

Your garden waste (30:1), green wood (25:1) and vegetable scraps (25:1) you mention are already at the right ratio on their own! To make these heat up nice and fast, add chicken manure to these ingredients.

Grass clippings (20:1) which are high in nitrogen need some material high in carbon such as dry leaves (60:1), so mix 1 bucket of grass clippings with two buckets of leaves.

The Rabbit poo and wee, mixed with sawdust is already a blend of nitrogen and carbon rich materials, that’s pretty balanced. If there’s too much sawdust in there, add some of your chicken manure to it to increase the nitrogen content.

Hi Blackthorn.
I have started trying out a hot compost heap & have a couple of questions. I have had to create the pile over a cple wks (the space for the pile is about a metre square) due to having the correct materials ready. Will this have made a massive difference and will it still be able together hot. measured the temp 2 days ago it was 30, I then added more layers the next day measured temp again and it was at 40 degrees. It is about 700 cm high now so still going..
With layering, should my carbon (dry layers) be thicker than my nitrogen (green) layers to get the correct carbon: nitrogen ratio or the other way round. Also how thick should my layers be?
Seems to be taking me a lot longer than an hour to create a heap, although I don’t have a shredder so doing it all by hand…
I live in the UK so getting colder here now, I was going to cover with tarpaulin,..should I do this on all sides or is the top and front enough?
Appreciate the help, it is a very exciting process.
Regards,
Sally

Thanks for the informative site. I would like to share my hot composting experiences with you, although I use a different system that takes a bit longer than 18 days and requires no turning. I live in a very windy part of South Africa, so I’ve made a 1m square chicken wire support and lined the sides (but not the bottom) with heavy-duty black builder’s plastic.

I put garden waste and food scraps into this over a period of a few weeks, adding woody material from a previous compost heap and keeping it moist. I don’t have any manure but I have plenty of leaves, grass cuttings, hedge trimmings and weeds. I usually cut the stalks and big pieces up with pruning shears before adding. I cover it loosely with plastic while the heap is growing and it generates some heat.

When it is full (about 90cm high) I add a thick 30cm layer of grass cuttings mixed with dry leaves, water it well and cover it tightly with black plastic weighed down with stones. It gets extremely hot and gives off steam if I lift the cover and dig down with a trowel. After a matter of days or a few weeks it cools down and turns into good black compost all the way through. The earthworms multiply the longer I leave it.

The time taken varies, depending on the season (we have cold wet winters and hot dry summers – I will time it more exactly in future). I used to turn it occasionally but it didn’t seem to speed things up much, and I’m nearing 70, so it’s a good method for an energetic geriatric. I live in a complex built on clay, so this is a valuable resource for my patch of garden and the others I look after.

hi , i am in india and think your explanations are very good.you have taken a lot of effort. can you please answer one question. after we have made the pile and turned it ,can i water it again if i feel it is too dry.will appreciate an answer.. thank you ..

Hi, I had been trying to get my compost to heat up for a couple of months and was getting a bit demoralized. I totally underestimated the amount of nitrogen that I needed to add – or maybe I didn’t realize how much carbon material I had put into the piles.

Anyway, a week ago I added a bag of Blood and Bone (about 5kg) into each compost pile and Voila! Worked like magic.I can’t tell you how excited I was to see the steam pouring off of the piles.

I am Irish and live in Poland. At this moment, I have about 8 large piles of horse bedding that I have been composting since around april. The latest pile is about 2 or 3 cubic metres in volume. I wont turn it because it is a lot of work although I do check it to see if it is hot. Occasionally, I have removed some material from the bottom outer section and even that has been hot. I intend to use the composted material for raised beds. I havent used tarps nor any sheets to retain heat etc but I have used soil. I dug a trench around some of the compost heaps to a spades depth and width and used that soil to form a layer coating on the heaps. It isnt a perfect cover but 80 percentish. Recently, I tried to use a cover comprising of some hay and dried garden grass etc that had been forgotten nearby a ditch and it seems to work. It can help to retain moisture. On some heaps the soil is black but on others the soil is just like greyish soil. Hopefully, I will have about 5 or 6 cubic metres when it is ready to use by september – october.

Thanks for this really interesting blog and summary.
I am working for the IUCN as a Marine Biologist on a Resort in Maldives. The situation with the organic waste is quite sad: Every resort and every local island is throwing the entire organic waste into the ocean, which is detrimental for coral reefs. I am looking for a project that eventually also has financial support to find a solution for this. Herein I am looking for opinions, specialists and ideas. The conditions are a bit difficult: high amounts of different organic waste (raw material as well as cooked left overs) (about 500-1000 kg a day), tropical conditions, great limitation of space, smell needs to be minimized. i am looking for a way to turn it into soil rather than bio-gas, because also soil is limited in Maldives. Eventually every resort and local island could start producing a small amount of vegetables and fruits if we would find the right solution.
I am wondering if you would be interested to do some consultation for me or if you have any further contacts that could help me further in this matter.

I am trying to have a pile of compost for heat. I will be using straw, wood chips, vegtables matter, grass , and urine. My goal is to have a hot pile for as long as possible. So I am asking how long can I keep a pile going at the best possible heat. I am going to try heating my house using water transfer to radistors, for a 6 months. Will I need 2 piles three months each? What will be the best mix. And are these ratios by weight or volume? I would ghuess weight. But I want to hear it said. Thanks , please e-mail me

Making compost is one thing, building a compost powered hot water system is another, and that would be another whole article in itself! If you do an internet search on “hot compost showers” there are a few videos and articles that may be helpful. For a long, slow release of heat that lasts for months it appears that some people have used very large scale anaerobic systems which produce very poor compost because they use only wood chips rather than fast heating aerobic systems like this which use a variety of ingredients and produce a very rich compost.

i have been trying hot composting but something doesnt feel rite. its been over a month but the compost pile is still hot around 140F. The color has changed to blackish brown and smells sweet n earthy. I used sugar cane trash, rapseed trash and banana leaves as carbon source and for nitrogen i used food scraps and cow manure. C:N ration is around 30.1 and i always keep the pile covered with plastic. where am i going wrong? help would be appreciated.

I am now on day 9 of my hot composting but the pile has significantly cooled. When I turned the pile yesterday it was warm and steaming a little in the centre but it wasn’t hot. How do I get it back up to temperature?

As mentioned in the article, if it starts to cool down, you can heat up the compost by adding a handful of blood & bone fertiliser per pitchfork when turning. You can add ANY rich nitrogen source to make the compost heap heat up again. Any animal manure will work.

See the instructions listed under Day 4 – “Ensure that moisture stays constant. Put gloves on and squeeze a handful of the compost materials, should only release one drop of water, or almost drips a drop.”

Hi there,
I’m trying to compost just flowers here in my locality. Here in India we have lots of temples and a lots of flowers are offered there , even some temples generate 10-20 ton every day, and they simply throw it. I’m planning to make compost and colors out of it.
Can you tell what I have to do when I’ll be only composting flowers like Marigold, rose, etc.
And how will I manage the composting ‘coz I’ll be getting 10-20 tonnes of flowers daily!
Suggestions are appreciated :)

Hi just finished my first compost pile and have a lot more material for another one. Can you please tell me how much comfrey should I put in the middle of the pile? I also added vegetable scraps near the middle of the pole as well.

I watered the pile once I finished and am a bit anxious that it may not have soaked through the whole pile – water was running out the bottom but I have used leaves that where on my driveway and some had started rotting already (very long driveway). Should I keep watering the pile each day? I am on day 1 of the 18 day composting system.

I’ve never had much luck with hot composting, but my recent attempt (following your instructions) got me closer to success than I had before. Like Sara who commented above, I think this time around I had an issue with the compost heap cooling too soon, possibly because the carbon sources (including broken up twigs & woody vines, as well as some newspaper/cardboard) were too large or too imbalanced to the nitrogen that I added (including chook manure, kitchen scraps, fresh grass clippings). It’s been over 18 days but the carbon rich materials still haven’t broken down, the temperature has dropped and a few worms have been moving into the heap.

I’m itching to get this compost into the garden asap so I can get my summer veggies growing, so was hoping for some advice. Do you think it would be better for me to mix a nitrogen rich source (i.e. chicken manure) into the heap and keep it going for another week or so, or do you think it’d be possible to apply the half-broken down (still quite woody) compost along with additional chook manure directly to the garden beds now? The latter option appeals to my impatience, but I’m worried that nitrogen draw down might slow the growth of my summer seedlings. Would you recommend that I be patient and continue the composting above ground, or can I get away with digging it in now?

The best way to make any compost is to break up your materials really well. Large chunks of carbon-rich material don’t break down very easily, there is very little surface area for the bacteria to act on. By breaking up materials you increase their surface area which exposes more material for the bacteria to work on.

If you add compost with woody material that is not broken down into your soil, the woody material will continue to break down in your soil, but the bacteria will need to draw the nitrogen out of your soil to compost it, which means your plants won’t get to take up the nitrogen, and suffer from nitrogen deficiency. This phenomenon is called ‘nitrogen draw-down’. Don’t do it, you’ll starve your plants of nitrogen and they won’t grow very well!

Your best option is to use the material again, doing another 18 day hot compost by adding more nitrogen containing material. The idea of using it your incomplete compost as is with lots of woody material in it with chicken manure is not a worthwhile choice because whenever you add chicken manure to your soil you need to wait for a minimum of a week, preferably two weeks, before you planting in the soil, as you can burn the roots of plants and seedlings, and it takes the bacteria time to start acting on the manure to break it down so the nutrients become available to the plant. Plants can’t feed on manure, they feed on the nutrients released from manure by bacteria. Either wait 14 days and still have a problem because the woody material in your soil that won’t all break down, or do another 18 day compost. It’s worth the extra 4 days!

If you’re really feeling lazy, just get a yourself soil sieve, or make one out of wire mesh, and sift your compost to separate all the course material out. Use the fine compost that has broken down in your garden, and put all the coarse material that has not broken down to one side, break it up much finer, and use it in your next compost attempt.

My own further observations on the hot compost heap that cools too soon:

Following Angelo’s advice about my similar problem and some trial and error, I’ve found that I need a slightly higher proportion of nitrogenous materials to keep the heap hot and complete the process in three to four weeks. (Perhaps this is because some of the carbon-containing materials I’m composting are at the higher end of the C:N ratio). I re-activated my heap that cooled too soon with more manure and lawn clippings, and some blood and bone, and ended up with a fine, high quality compost at the end.

Over a number of heaps, I’ve found that adding a good portion of fresh manure (rather than the dry, powdery, more “composted” stuff) makes a huge difference to the success of the process for me. (I’ve been using fresh sheep manure). In my most recent heap, I used fine, more composted commercially bagged chicken manure and it didn’t work so well. In theory, if the C:N ratio is right the heap should heat up and stay hot as expected, but for some reason in practice the fresh manure seems to get the whole thing hot and going far better for me than without it.

I would reinforce that the other thing that seems to make a big difference is keeping the heap evenly moist. I keep mine loosely covered with black plastic to keep out any heavy rain (to avoid cooling it too much by becoming waterlogged – also a contributor to my heap that cooled too soon), and to keep the moisture and heat in. In a sunny spot with the black plastic on, I’ve found the outside of the pile stays much more moist and composts better than if the heap is open and dries out somewhat on the outside. (I am composting in Melbourne, Australia – the black plastic may be superfluous in warmer and/or more humid climates).

Em – keep at it! The process may require some fine tuning and trial and error until it works best for you and the materials you’re using, but it’s worth it for the lovely fine, rich compost at the end. An alternative to sieving your compost may be to chop up the woodier material (eg woody vines) a bit more with a spade and return it to the heap, depending on how woody it is overall.

Just finished sifting the results of my second hot compost pile following your recipe. Beautiful rich material :) Setting up for my next pile. I shred all my materials using a leaf shredder. Is your 1/3 green to 2/3 brown more correct for unshredded materials where the brown has a lot of air spaces in it? Should I be looking more at half green to half brown?

Also I have kitchen waste with some scrunched up paper in it from a cold compost bin with has built up over the past 8 months. I would like to add this to my hot compost as I really need to use everything to add bulk. Do I consider this to be green in my ratio calculations or neutral? That is, layer it in thinly but don’t count it in my green layer to brown layer ratio?

You’re welcome!
The ratio of 1/3 green to 2/3 brown stays the same whether shredded or unshredded, the brown material may have more air in it, but the green material is just filled with water instead.
If your kitchen waste has a lot of paper in it, as per the ratio just mentioned, then it’s balanced in its C:N ratio, if there’s not much paper, treat it as ‘green’.

Hot composting can break down a lot of contaminants in composting materials that can be broken down, and the organic matter is capable of binding many contaminants that don’t readily break down, locking them up.

Another question, sorry, should have thought of all this for my first message. My brown is dried leaves, shredded dry sticks, dry bambo leaves and stems. I have more bambo than leaves or sticks. Is this an issue? Is bambo an ok ingredient?

Bamboo is a grass, and it is also a woody material. Woody materials contain lignin, which breaks down to create the most stable humus. Bamboo is a great ingredient to add to your compost if it is chopped up finely or mulched.

Thank you Angelo, it’s so good to have your expert input – my delicious hot compost pile is now doing it’s thing it has a wide range of ingredients including a good mix of shredded bamboo – very exciting! Happy holidays in the garden to you.

Yes, cat hair and human hair can be composted, it’s actually very high in nitrogen so it counts as ‘greens’.
If you brush your cat, collect the hair and hot compost it. Consider what happens in nature, when animals walk around in their natural habitat, they drop their hair. When then moult going from the cool to warm seasons, they lose a lot of hair, which falls to the ground and is broken down along with all the leaves and other plant material.

Please DO NOT use mouse droppings, they may carry hantavirus which causes Hantavirus Pulmonary Syndrome (HPS) in humans, a severe respiratory disease which can be fatal. The disease is spread by breathing in dust that is contaminated with rodent urine or droppings, or through direct contact with rodents or their urine and droppings. It is not worth the risk for the tiny for the tiny amount of nitrogen containing material you would get.

Ah, not Mouse. Moose. We have a land with a bunch of those big fellas and when we go snow shoeing, there’s often those huge pile of Moose poo and sometime it’s still steaming. It makes us both relieved and pissed off because sseeing a Moose is really awesome… except if it decides to charge you. You can never outrun a Moose… ever.

We have kangaroos here instead, luckily they aren’t found near our urban areas! Our biggest ones, the Red kangaroos, according to national geographic, can reach speeds of over 35 miles (56 km) an hour, and they can cover 25 feet (8 m) in a single leap and can jump 6 feet (1.8 m) high. They can weigh up to 200 lbs (90 kg). They don’t run, they hop, and can jump over fences easily. Moose are definitely scarier though! :)

Hi,
i have recently attempted your hot composting method and have found it very useful and the concept of having compost in 18 days very exciting! today is day four for my compost, and i think i may have added too much green products. i made the pile out of horse manure, a little cow manure, paper, lawn clippings, kitchen scraps and a little garden waste. on turning it today, i have found that it has heated up but…i think it is a bit too wet. i then proceeded to add more dry garden waste. should i just wait a couple of days before adding anything else? and if i should add anything else to increase the carbon, should it only be sawdust as you mentioned?
kind regard
zinette

Was your compost pile really too wet? I’ve described how to test if it is in the Day 4 instructions – “Ensure that moisture stays constant. Put gloves on and squeeze a handful of the compost materials, should only release one drop of water, or almost drips a drop.” In that section I also mention how to fix the problem, which doesn’t involve adding extra material!

If you’ve added some dry material to fix the problem with the pile being too wet, and there is enough nitrogen-rich material, than that’s all you have to do. Just continue following the steps. Hope this helps!

When the hot composting process takes place, oxygen is required by the aerobic bacteria. In tiny spots here and there within the compost pile where oxygen momentarily is all used up, the process reverts to anaerobic breakdown and this is when methane and nitrous oxide are produced.

A highly aerobic system such as the hot composting system minimises the production of these gases, whereas an purposefully built anaerobic digester designed to capture methane gas as a fuel intentionally maximises methane production.

Let me put this in perspective though – methane is a natural part of the carbon cycle and is produced naturally under conditions of anaerobic decomposition, in swamps, in the breakdown of plant material on forest floors, everywhere where carbon containing material (all living things) break down in the absence of oxygen, including us when we are buried!

There is no issue with natural processes creating methane, it is produced as part of nature’s essential processes of the carbon cycle which perpetuate life. People fussing over flatulent cows are misguided and missing the point. Do we kill all the cows because they have wind??? What we need to take issue with is anthropogenic greenhouse emissions, the release of greenhouse gases through human activity which does NOI sustain life, and which is non-essential, that is the real problem!

I was curious about the down side, because I feel there is a very considerable up side that seems to be slightly overlooked – unless I have got it wrong. We agree that cold composting drastically reduces the volume of the compost heap over time. This is because the contents are lost as carbon dioxide, water and small amounts of nitrogen gases. The fact that the volume of a hot pile is not reduced in the same way, surely, indicates much reduced losses of CO2 etc.

In addition to retaining much higher levels of carbon and nitrogen the Berkeley method appears to be preferable to cold composting in terms of the net greenhouse gases emitted. Is this how you see it or have I overlooked something?

Yes, that’s right, the hot composting method is a highly aerobic process which does not decrease in volume like cold composting, and loses the least nitrogen and produces the least methane of all the composting methods!

I am enthusiast new gardener and to save bucks I tried your idea and gather
1. Straws (brown Material)
2. Goat Pallet (Manure)
3. Kitchen Waste (Green Material)
4. Chicken beat (Manure)
5. Some leaves
And follow the instructions exactly as you mentioned starting from 05th Feb 2015. All was good and accordingly as told in the article but then suddenly heat vanish and all almost cooled down and I can still see all the coarse brown material as is (in kitchen waste I used Peanut shells which are still almost the same nothing broken and goat pallet still round and running like a ball)
Today (5th Mar 2015) it is 30th day. I do not have Thermometer available for now so don’t know the exact temperature but for sure while turning I cannot feel any heat nor can see the smoke and it appear to be cooled down but still I can separate straws, peanut shells, goat pallet etc but no green material can be differentiated. So what to do now? is it ready? or I have to do something like grinding? I do not have garden so I am doing all this on my roof top and I have all the pictures available and can share if you like.
Awaiting for your guidance.
Thanks,
Jawad

I’ve just read through all the comments and it sounds like there was not enough green stuff (nitrogen) to start with… You could try adding a few handfuls of blood and bone or some more high nitrogen manure…. I defer to the experts who I am sure will comment soon but maybe after so many days ‘cool’ it might be too late to bring it back to life…?

It is now almost a week in cool state – I do have a bucket of green material available (kitchen scrap) which can create a layer or two so should I add that and give it a try? and should I water all again to made it wet will that help?

If that cannot bring back to life (finished compost) than what alternate options I do have? What can I do with that stuff to make it useful somehow so that it cannot be a complete pile of waste.
Thanking you in anticipation for all the help one can provide.

If the compost heap has cooled right down, it means you did not have enough nitrogen-containing materials to begin with.
It is best to start a new hot compost heap, and you can use your material that is not completely broken down as the carbon-containing material in the new compost heap.

Thanks Angelo, Few more questions just to make sure I do not end up on wrong end.
Following material I need to use to create new heap
1. Brown Material (current compost heap)
2. Cow / Chicken / Goat manure
3. Kitchen scrap / Grass / leaves (Green Material)
4. Water them to made it all wet and do I need to water them again while turning?
5. Anything else to add?

Sorry for asking such basics questions but just to make it successful this time I need to know these.

It is now almost a week in cool state – I do have a bucket of green material available (kitchen scrap) which can create a layer or two so should I add that and give it a try? and should I water all again to made it wet will that help?

Hello Angelo,
Thank you for your inspiring and helpful instructions.
We need your advise.
Our compost is on its 17th day.
*The size of our pile is not exactly 1 m3 (about 0,60-0,70m3)
*It smells very good
*The weather temperature is around 8-20 celcius. When it rains we cover the pile.
*We can observe the decomposing process, the colour is getting darker each day but
Its COLD :) On the very first days it was getting hot but somehow the temperature didnt rise again.

Does it look ready? If the compost has broken down into a really fine, dark mix that smells nice and earthy where you really can’t recognise the original ingredients, that’s what hot compost looks like when it’s completed. It should stay for longer than just one day though.

Thank you for your quick response Angelo. I am sorry :) I should have given you more details about the situation. They started to brake down but we still can recongnise some of them.? We think that the reason is the size of the pile, as I wrote you yesterday it’s less than 1m3. Is it okey to add something more at this point?

It sounds like your compost ran out of nitrogen and cooled down. As per my reply to a similar question earlier to Jawad, “It is best to start a new hot compost heap, and you can use your material that is not completely broken down as the carbon-containing material in the new compost heap.” Just add more nitrogen containing materials and it should work this time around. Try to get that critical size of one cubic metre or more this time though.

Thank you sharing this article
Built my first hot compositing heap just 10 days ago using this 18 day method temp is steady at 55 deg C. it is made up of cardboard leaves, grass clipping and coffee grounds. we did have an issue at day 6 with smell and a decrease in size, which we got from it has too much nitrogen, that we corrected quickly.

It is built in wheel bin that has been modified to compensate for the width restriction. It is a flow through system with a large access port at the bottom for turning. We use a metal rod placed on top of the compost heap to know when it has completely turned ( we see the rod in the bottom ).
We are using this method to make compost but also heat our underground walipini polytunnel in spring this year and hopefully autumn and winter.

I live in the city and have a difficult time in finding enough leaves, weeds, etc. (let alone animal manure)… Anyway, I have finally managed to get a heap of only around 90cm tall. Must I get it up to 1.5 m tall? Also, I forgot to cover the heap and it’s raining quite heavily (I’ve just started creating the heap). What should I do now? Thanks

I love hot composting myself. The best way I have found to get large amounts of material to make a big batch is by bagging by grass clippings mixed with leaves. That combination of fresh clippings with shredded leaves is dynamite in a hot compost pile. Mowing leaves and grass together. It gets hot quickly, it’s free, and as long as the weather isn’t really cold (sub-freezing) it finishes in two weeks every time. Great topic!